Always stating the QPL (in)compatibility in GPLed code?
Posted 20 Jun 2000 at 16:28 UTC by Raphael
At the risk of starting yet another controversy about the KDE/Qt
licensing issues, here is a proposal to move away from the current
status quo which does not benefit anybody (Debian cannot include
KDE, and the KDE team has to spend precious time replying to
endless questions)... The solution is to raise the awareness of the
GPL/QPL compatibility problems by always including a statement
about the QPL in every GPLed package. If this issue cannot be
ignored anymore and the Linux distributors cannot rely on
ignorance or silence, then maybe things will start moving and
eventually KDE will have a license that allows it to be
So far, the Linux distributions including and promoting KDE
(Mandrake, SuSE, Corel and many others by now) have ignored the
incompatibility between QPL and GPL because they expect that nobody
will sue them. Some of them also assume that distributing KDE is legal
because they believe that the authors of the GPLed code that has been
re-used by the KDE project would not be opposed to that and have
given their unwritten consent to have their code distributed together
with Qt or QPLed code.
If the KDE team does not put some effort into clarifying the
issues and adding the "QPL compatibility clause" in the KDE core and
applications, maybe they could be encouraged to do it if many other
software packages released under the GPL start including a statement
about their acceptance (or rejection) of the QPL. This would raise the
awareness of the (in)compatibility issues between the GPL and QPL among
users, and the major Linux distributions could not ignore this
So here is a modest proposal:
If you like the QPL:
If you are the author of a GPLed software package (or if you are one
of the authors and all other authors and contributors agree) and you
would not mind having your program distributed together with Qt,
then include something like the following statement in every source
file, before or after the reference to the GPL:
As a special exception, you have permission to link this program
with the Qt library and distribute executables, as long as you
follow the requirements of the GNU GPL in regard to all of the
software in the executable aside from Qt.
(this is the wording suggested by the FSF) or with this statement,
suggested on the Debian pages:
... with the additional permission that it may be
linked against Troll Tech's Qt library, and distributed, without the
GPL applying to Qt.
If you do not like the QPL:
On the other hand, if you do not agree with the licensing terms
of Qt, or if at least one of the contributors disagrees and her code
cannot be replaced easily, then include something like this:
Reminder: sections 2.b. and 7. of the GPL forbid the distribution of a
compiled program that is derived from this code and from any other
code that is distributed under a license that is not compatible with
the GPL. One example is the Qt library version 1.x or 2.x released
under the Q Public Licence (QPL) version 1.0, because it adds
restrictions that are not allowed under the GPL. If a future version
of the QPL becomes compatible with the GPL, then this limitation
would not exist.
Or this shorter version (which could unfortunately be taken as
flamebait if it is not understood correctly):
Reminder: The GPL and the Q Public License (QPL) version 1.0 are
incompatible with each other, so you are not allowed to distribute a
compiled executable derived from this code and from the Qt libraries.
Including one of these statements in the license of many programs
would make the problem much more visible, and hopefully encourage
the KDE team or Troll Tech to do something about it. It would also
prevent the major Linux distributions from ignoring the problem
Who should do it?
If possible, we should encourage as many software authors as
possible to include a clear statement about the QPL compatibility in
their software (either pro or against, it doesn't matter). Even if the
software is not related to any graphical interfaces or widget sets.
For those who like the QPL, this would make it clear that their
code is QPL-friendly and can be distributed legally without violating
the GPL. Eventually, all of the KDE code should be released under
such a license (GPL + Qt exception). I think that most of the Open
Source developers would fall in this category, so a lot of code could
become compatible with Qt.
For those who do not like the QPL and prefer to be strict about
the GPL, adding some statement about the QPL would make users
aware of the incompatibility that has always existed between the
GPL and the QPL and that has been ignored so far. It would also
serve as a warning for developers who are considering to re-use this
GPLed code in other programs. Maybe they will reject the code
because of that and be forced to re-implement it (yes, the GPL does
have some restrictions) but this is better than ignoring the issues
and being bitten later.
QPL, posted 20 Jun 2000 at 18:58 UTC by jrennie »
For refernce the QPL can be found at http://www.trolltech.com/products/download/freelicense/license.html.
I just read over the QPL. It is awfully strange. It allows you to
distributed modified binaries conditioned on you guaranteeing free
access to the source code of the software along with any modifications.
However, it does not grant you the authority/power to distribute the
original source code, only your personal modifications. Is this where
all the confusion stems from?
Before Troll Tech rectified (largely, that is) the issue with the free
version of Qt, there was a major concern about a non-free licensed
library being part of what could be a core functionality to any Open
Sourced library- not to mention that it was technically a violation of
the GPL license to distribute anything but the KDE sources (This same
issue we're talking about right now has been lurking since the
beginnings of KDE and you'd get fiercely and mercilessly
flamed into submission on mail or news lists if you brought up the
issue- I know, I've been on the recieving end of some of it back before
the 1.0 release of KDE.). I've been led to believe from several people
on both the KDE and GNOME side of the fence that this issue was one of
the things that caused the GNOME project to come into existance, along
with some design decisions in KDE that the GNOME people didn't agree
with (I side with the GNOME team on that regard, but KDE's still
awesome.). So, what's the situation now? Troll Tech, made the license
more free, making it palatable to the Open Source community, but didn't
go far enough, making a license that is incompatible with the GPL and
LGPL- which then prohibits the distribution of many of the KDE binaries,
per the GPL. Seems to me that we're largely in the same boat as before,
with only a slightly more palatable license on Qt.
needs to migrate things to Harmony, GTK--, or Fltk, the KDE team needs
to change all all of their licensing to be something other than
GPL/LGPL for all packages, or Troll Tech needs to revise, yet again,
their license to be compatible with the GPL/LGPL. Only the copyright
holders may release binaries given the current situation- anyone else
(incl. the KDE team themselves, in at least some of the cases within
KDE...) can be construed as a copyright violation.
Finally..., posted 21 Jun 2000 at 02:18 UTC by sab39 »
Finally... A post on this issue that's clearly made by someone who has
at least a basic understanding of the issue. Thank you for restoring my
faith in humanity ;)
PS My own personal opinion is that someone should come up with a license
that provides GPL-style protection against use in non-free software, but
that always behaved like the LGPL for software that was free (even if it
was GPL-incompatible). I have some ideas on how such a license could be
written - in fact, I had a copy drafted until I lost it to a hard-drive
crash. I plan on re-writing it, and when I do, I'll post or link to it
from my diary. I'd be interested in feedback on this idea. This wouldn't
help KDE unless they re-licensed their software under my license, but it
would provide a choice for people who want the protection of the GPL
without the incompatibilities.
So, the way to decide the discussion about whether the QPL and the GPL
are incompatible is to just say it many times in many places?
You are giving the people who believe the QPL and the GPL are not
incompatible, the chance of... not licensing under the GPL (because
GPL+exception != GPL) dammit, if I write software that requires Qt, of
course it's meant to be used with Qt. If you are not sure, ask me, I'll
clarify!. But I will not put it in the license, because the license I
use IS THE GPL.
If you believe the software author's interpretation is the important
one, then that interpretation (say, mine) in itself is enough, without
changing the license.
If you believe that interpretation is not important, tacking at the end
of the license a non-binding reminder like "BTW: you can't do that"
is just pointless.
Either way, you achieve nothing, except giving the developer a chance to
not release under the GPL, which he already has. Pointless again.
ralsina: If you believe that the GPL and QPL are compatible, then by
all means place a note at the end of your license (not an
exception) which says something like "Note: In the opinion of the
copyright holder, this license is not incompatible with the Q Public
License under which Qt is released. You may, of course, distribute this
software linked with Qt."
This would be adequate for Debian to include your software, because a
firm statement from the copyright holder overrules the license (even for
those who believe the two are incompatible by default). Yes, it's kind
of silly that you have to say it when you wrote software requiring Qt in
the first place. But Debian have said that this would be adequate; isn't
it worth making a statement like that (which obviously expresses how you
feel anyway) just to end this stupid flamewar once and for all?
As to why it needs to be stated explicitly - my understanding
(which could be way off) is that Debian feel that they need
something that they could point to if they or any of their
distributors ever ended up in legal hot water over this. A statement
from the copyright holder would at least provide some sort of legal
assurance that nobody is going to be sued. I can sympathize with that
Perhaps that would be the real solution for KDE itself - nobody from
KDE needs to back down - they can continue to sincerely claim that there
was never any problem with their choice of license, and that they're
just adding this comment to satisfy the ridiculous claims of Debian
folks. And the Debian people wouldn't need to back down either - they
can continue to believe that there was a problem, and that the adding of
this statement solved it. All that, just by KDE just putting a line in
their licenses stating what they believe to be obvious anyway!
There are, of course, still issues with other people whose code has
been used in KDE, who may have not believed that the two licenses are
compatible (the KDE postscript viewer is the canonical example). But
perhaps those people could head off the problem in advance by adding
either an exception, or a statement that they don't believe there's a
problem, pro-actively to their licenses.
Will it ever happen? I don't know. It seems to be nothing but
stubbornness keeping the issue alive - it's SO easy to solve.
Not for a second. Debian has in the past removed KDE software from their
distro that is not under the GPL, and is thus not in a license conflict.
I am talking about kdelibs, of course. And before a Debian guy comes up
and asks: AFAIK, yes, kdelibs for a pre-alpha version of KDE2, that
linked to the QPLd Qt 2.0, and that was undisputedly under the LGPL, was
uploaded by a registered Debian developer to debian.org. It was deleted.
Why should I (or anyone else) believe this noticewill make any
difference whatsoever regarding Debian? It's just a sad state of
If Debian wants that comment in any software I write, it's simple to
get. Email me, and ask me:
"Do you interpret the license to your software as allowing linking to
They will get an answer that says "yes", and they can save it in the
.deb for all I care.
Roberto, I know you are cool with the linkage (we've had
over similar things in the past...)- but what about some of the authors
of things that the KDE team derived from other GPL/LGPLed projects (such
As for Debian checking with everyone; that's the
KDE team's job, not theirs- don't pan them for not including the
packages if they've got issues with the way you're doing things. If
you've got ambiguities in your licensing, they choose to omit things;
which is what I see going on here. The issue is as I said it was;
there's a more than merely percieved incompatibility with the licenses
involved and nobody that could fix this mess is really doing
anything substantive about it.
Its obvious (though perhaps legally ambiguous) that KDE developers who
write code under the GPL and link it to Qt intend to allow distribution
of their software. What isn't clear is when GPLed code by a third party
is integrated into a KDE program. Qt's license is incompatible with the
GPL - and a lot of people who license their code under the GPL have an
issue with Qt's license. Apart from the legal issues its really really
rude to link their code to Qt. If people did that with my code I would
be really insulted - at least as insulted as if my code was ripped of by
some proprietary software people - we're meant to be a community!
Please, if you're a KDE or Qt developer refrain from KDEifying GPLed
programs or integrating GPLed code in your software.
Because of section 3, which reads.
3. You may opt to apply the terms of the ordinary GNU General Public
License instead of this License to a given copy of the Library. To do
this, you must alter all the notices that refer to this License, so
that they refer to the ordinary GNU General Public License, version 2,
instead of to this License. (If a newer version than version 2 of the
ordinary GNU General Public License has appeared, then you can specify
that version instead if you wish.) Do not make any other change in
If the LGPLed library is linked against a QPL library, I can't do that,
as GPL is incompatible with QPL. Therefore, the licence is void.
Misc replies, posted 22 Jun 2000 at 17:51 UTC by ralsina »
About whether clearing up the licensing is my job or Debian's or
I don't care. I *do not* believe my license is ambiguous. Why should I
fix something I don't believe is broken? If Debian believes its broken,
they can EASILY check if it is broken by asking the licensor (say, in
some cases, me). If that is not their job, what is?
About KDE and foreign GPL code.
The only application in KDE2 that has foreign GPL code is, AFAIK,
kghostview. And I am not positive about whether permission was granted
for it or not. Again, that is easy to fix: 2 emails.
In KDE1, the only other foreign GPL code was in kvt.
Even if Debian, for instance, doesn't feel they must bother sending
three emails, they still have a better solution than removing 50
applications: remove 2.
About incompatibility between LGPL and QPL.
Your post shows ignorance of basic licensing issues.
People doesn't violate licenses: ACTIONS violate licenses.
Changing the license of a piece of code to GPL is not an action that
violates any of the involved licenses.
It is possible that after you switch to GPL, you end with code that you
can no longer distribute because THAT ACTION would violate the license.
The solution is, of course, not switch to GPL if you ever intend to
redistribute the code, or not redistribute after you switch. Both
courses of action are perfectly legal, IMHO, IANAL.
's libwv code
was integrated into KOffice - and he doesn't seem happy
about it. If
KDE's flagship app is infected, what else is as well?
Maybe someone assumed wrongly that it was under LGPL. Mistakes do
So, the way to decide the discussion about whether the
QPL and the GPL are incompatible is to just say it many times in many
My proposal was not about deciding if the QPL and GPL are compatible
or not. This was a proposal for how to spread the information about the
fact that they are incompatible if you intend to distribute a compiled
program that includes code covered by the GPL and QPL.
Read section 2.b. of the GPL: it states that any work (e.g. the
compiled program) that contains code covered by the GPL must be licensed
as a whole under the GPL. This is the "viral" part of the GPL. This
implies that if some parts of the code are covered by another license
than the GPL, then their license must be compatible with the GPL in
order to allow the re-licensing. If you also read section 7. of the
GPL, you will see that you are not allowed to distribute your work if
some obligations (e.g. other license) prevent you from fulfilling all
the conditions of the GPL. The QPL imposes some restrictions that are
not allowed under the GPL (distribution of patches), so with the QPL is
incompatible with the GPL.
There is no problem as long as you are distributing your GPLed
program as source code, as long as it does not include any code covered
the QPL. But if you compile your program, link it with the QPLed Qt
library and distribute the binaries, then you are violating the GPL
because the whole package includes code covered by the QPL and GPL and
the GPL forces you to distribute this work under its own conditions,
which cannot be done because of the QPL restrictions.
After having read many discussions about this (KDE archives, Debian
pages, RMS explanations, Freshmeat editorial, ...), I think that the
fact that the two licenses are incompatible does not need to be proven
anymore. Even a large part of the KDE developers admit this, but at the
same time they say (and they are right) that most of the code written
for KDE was written with the implicit assumption that the GPL was
extended to include the compatibility with the QPL.
So the problem that I was trying to solve here was not to explain why
the licenses are incompatible (this has been discussed many times in
many places), but to encourage the authors of GPLed software to include
a clear statement about whether or not their code can be used in a
program that has to be linked with Qt. Many people are not aware of the
incompatibility that exists between the QPL and GPL, so stating this
explicitely in many places (by adding an exception that allows linking
with Qt or by explaining the problem) would help and may encourage
developers to think twice about the licensing issues. Actually, I am
always surprised about the number of developers who are surprised when
they discover that the GPL is more restrictive than they thought,
because this "viral clause" is not easy to satisfy. Some of them switch
to another license such as the BSD license or the Mozilla licence after
discovering the problems of the GPL. Well, so be it. But it is better
to be aware of these problems before it is too late.
If the Qt exception is added to many programs (or a statement
explaining why the code cannot be linked with Qt, for those who choose
to be strictly GPL), then the information will spread and nobody will
silently ignore the problem. The current status quo is a very bad
rbrady - Sorry, even though I disagree with ralsina about most
aspects of this, I have to agree with him that you are wrong about the
LGPL. By your logic, the LGPL would not allow linking with proprietary
code either (which is exactly the point of the LGPL). Think about it -
the GPL is incompatible with that too.
To explain why this is so, you have to realize exactly what the
incompatibility with the GPL means. It does not mean that
distributing the KDE source is illegal (even though the KDE source
"requires" Qt to be useful). What it means is that distributing
something that is a "derived work" of both the KDE source and Qt (eg, a
binary of KDE compiled against Qt) is illegal.
How does this apply to the LGPL? Well, the LGPL states that you can
re-license the code under the GPL. It doesn't say that you have to be
able to get something useful if you do so. Perhaps you wanted to take
some code from kdelibs that didn't link with Qt, and use it in a
GPLd program. Or you wanted to port kdelibs to use gtk and release the
result under the GPL (which would be a strange choice of license, but
it's allowed). That's what the LGPL allows. It doesn't require that
changing the license to the GPL would result in something immediately
useful, just that you can do it.
Specifically, you can relicense the kdelibs source under the GPL with
no problem. The only problem is if you try to compile and distribute it
after doing so without removing Qt.
It would be a fact, if you could show a court decision saying it's a
I could even be convinced if you could show me a real lawyer who dares
put his name behind that opinion on the incompatibility.
Right now, what we have is blatant assertion by amateurs. I have argued
that a zillion times before with what seems like hundreds of them, and
the arguments are usually of very low quality (say ,"dude, the GPL
forbids putting extra restrictions on code linked to GPL code", when the
GPL says nothing like that).
I refuse to start that argument here again. I will only say, one more
time, that your opinion is not a fact, just like mine is not.
ralsina: Have you read Debian's stance on
KDE, which is the closest thing I know of to an "official" position
statement by the Debian project? Admittedly, it's probably not written
by a lawyer, but it does reference the specific clauses in the GPL and
QPL that appear to conflict. If you believe the two licenses do not
conflict, perhaps you could post a brief explanation of why you believe
this argument is flawed.
I'm genuinely interested, because you're the first person I've
actually encountered who believes this, and I'd really like to know what
the basis is for your belief.
I do agree that until a court or a lawyer states an opinion, nothing
can be taken to be unarguable fact. However, I've seen a number of
detailed arguments based on the text of the two licenses that seem to
indicate that they are incompatible; I've never seen an argument the
other way that even references the text of either license. This is the
primary reason that I believe the licenses are in conflict - I have been
unable to find a flaw in the logic of the people who claim they are
incompatible, and nobody who believes otherwise has even tried to point
out any flaws. You're welcome to be the first.
Debian's stance, posted 26 Jun 2000 at 12:39 UTC by ralsina »
Debian's stance is so flawed, it calls for the removal of kdelibs
because of a conflict between the GPL and the QPL.
That is only the most flagrant sign of that "document" being at least,
Then again, it is a document written by amateurs who hold a strong
ideological position. They are as far from being impartial as I am.
For other specific explanations of why I believe their arguments don't
hold water, I redirect you to deja.com and to the kde-licensing mailing
list. I have no interest on discussing the legalese again.
Old link, posted 26 Jun 2000 at 19:41 UTC by lordsutch »
ralsina: I believe the press release linked discusses the Qt1 (the Qt
Free Edition license) and KDE license conflict; hence, it does not
necessarily apply to this situation.
I think Joseph Carter's article speaks to the current situation, at
least for code (and bits thereof) that KDE appropriated from other
bottom line is you either buy his argument or you don't.
I generally agree with the point that stuff written by the KDE folks
(and not borrowed from other sources) probably is implicitly OK (mainly
because if the authors tried to sue a distributor, it would be pointed
out that they themselves linked the code against Qt). Whether or not
that leaves a usable system, I can't say.
lordsutch: the situation (alleged license incompatibility) is just the
same after the license change, according to any Debian guy I've read.
The situations are similar, but not the same. We now have an
unencumbered Qt that can be used with new code and with BSD code.
That, in and of itself, is a big win.
Saying nothing has changed is like saying WW1 and WW2 were the same
because both featured England and France fighting Germany.
FWIW, it seems easy enough to get around the conflict; you get KDE
separately from Qt. Since Qt is a standard component of Debian 2.2,
KDE is legal to use on Debian 2.2 if you don't get it from Debian. The
tricky part is making it legal for Debian to distribute it too.
A side issue..., posted 8 Jul 2000 at 18:15 UTC by argent »
I am increasingly tired of people writing software that requires either Gnome or KDE. Gnome and KDE are big packages, they take up a
lot of space and they take up a lot of my time keeping current with whatever version of Qt or Gtk I need for
Just what are the big advantages you get from KDE and Gnome that makes these heavy Microsoft-like library farms worthwhile?
A new editorial regarding the QPL-GPL issue has been posted on
I think that it summarizes the problems more clearly than most of the
other articles and discussions (including here, on Slashdot and on
Usenet). The comments are interesting too, although some of them
are missing their target because their authors did not fully
understand where the problems are. Here are a few things to
keep in mind while reading the editorial and the comments:
- There are no problems if you distribute a GPL'd program using Qt,
as long as you only distribute the source code. But the GPL
and QPL are incompatible if you distribute a compiled
executable, because it would be a derivative work (the
program uses the macros and types defined in the Qt header files)
and the GPL does not allow the distribution of derivative works unless
all parts of the work can be released under the GPL, with some
exceptions that are debated in the editorial.
- The GPL cannot force you to change the license of other pieces
of code and it cannot force you to use the code in some specific way,
but it can (and does) prevent you from re-destributing the
GPL'd code if you do not meet some conditions. One of these
conditions is that all parts of a derivative work must be
distributed under the GPL (see section 2b, the so-called
- If you are the author of a piece of code, you are free to distribute
it under any license and to change the license (for new versions) at
any time. However, this is only possible if you are the only copyright
holder. If you have used any code that was contributed by someone
else, then all contributors must agree on the new license.
This is a problem because some KDE applications (not many,
fortunately) have borrowed some code from other applications and
it is not easy to get the agreement on the "Qt exception" from all
authors and contributors.
- Some people say that we need a new version of the GPL without
the viral clause, because the current version is too restrictive and the
new one would solve the KDE problems. But they fail to understand
that some authors of GPL'd code do want this restriction, and chose
to release their code under the GPL precisely because of it (this does
not necessarily apply to all authors of GPL'd code, but those who are
in that category cannot be ignored).
Note: the LGPL is compatible with Qt and the QPL. The
LGPL is less restrictive than the GPL and allows linking with non-free
software. The title of one of my previous comments was incorrect (I
checked the article before posting, but I forgot to fix the title).
Sorry for the confustion.