The motivation for high performance software should be obvious. The less computational resources required by software, the cheaper hardware can made to support this software. The cheaper hardware is the more affordable it is to those with less wealth. This is something that completely bypasses the consideration of wealthy people in countries like the United States who enjoy an abundance of computing power. If the Free Software movement has any precepts regarding democracy, it should lower the computational hurdles of its software. An additional benefit to stagnating or decreasing computational needs is that computer hardware will have a longer life, and therefore the environmental impact of largely disposable computers will greatly decrease.
A good way to achieve performance in software is to make things simple. This idea did not originate with me, its echos can heard from the giants of computing. I'm in the process of rewriting my jpeg decoder. Analyzing the common types of images distributed, I was able to simplify the decoder in a way which yielded a 30% increase in performance. I now have less code, and a superior result. With simplicity comes transparency. Any software sympathetic to democracy should be transparent, that is the operation and structure should be as readily apparent as is possible.
I think an emphasis on democracy would be a positive direction for the Free Software movement. However, this would require a large break from the mainstream thought of how software should be created.