This letter shows an incredible ignorance about "free software." It's free as in "freedom" not free as in beer.
In very short: You give away your code because you used someone else's code (freely given) to build it, and they probably used someone else's code, and so on. And you're all using a license that requires free distribution.
The ability to use these tools makes my job easier - yes, my job. I work for a living, just like everybody else. The concept of somehow living off of making the world a better place is something you get from social workers, not programmers.
I try to give back to the community of free software developers because they've been very good to me. The closed-source folks have not been good to me. They just keep raising prices without making things any easier. So I steer my company away from them at every chance.
Not all cooperation is automatically communist. Open source software works because it benefits everyone involved. It's called enlightened self interest (For those of you from Rio Linda, that's a capitalist concept).
If you don't believe me, don't use open source. That's a simple freedom (there's the real free in free software!) closed-source companies don't want you to have.