Tonight I'm experimenting with 2D matrix code on Debian GNU/Linux. I found, grabbed, built and installed pyDataMatrixScanner  and it's dependencies. Getting the live image from my good old PCVC830 (ToUCam II) USB webcam displayed in a window was a matter of some more minutes (reading the README).
Now it get's interesting. Appears, that there is no python-virtkey package in Debian, that would be required for some advanced functionality. Ubuntu has it. When I queried the web about it, I got several hints on a bug  regarding packaging of this package resolved in Sept-2010. The very last comment of this bug report made me smile a lot:
> Thank to all developers for fix it...I'm Spanish and I'm 16...When I'm more old...I want to be like you.
> Thanks and regars!
I fixed this bug, and I am 14! ...
Edit1,2: Dependencies for Ubuntu Maverick's python-virtkey
can't be satisfied by Debian Squeeze. I ended up compiling
and installing my own python-virtkey from Maverick's
virtkey 0.60.0-0ubuntu2 source package. Note also,
that the needed pydmtx Python wrapper for libdmtx is hidden
in libdmtx-dev. You need to unpack source files in
/usr/share/doc/libdmtx-dev/examples/python/ and do a
python ./setup install manually (as root).