Developing free software as a profession?

For some time I was wondering how in the world, someone can devote all their time for developing free software. In planet earth, we need money for food, clothes and shelter. The couple of bloggers that I follow regularly are in fact full time bloggers (Jeffrey Friedl, Jeff Atwood), who also do some work to keep themselves busy, which (as of now) doesn't pay anything. So, recently when he wrote this blog, "Lightroom Plugin Development: What To Do When a Hobby Becomes Work", I was a bit disappointed.

One because, I wanted to be like them someday. Two because, atlast he was frustrated to work for free. I could understand his frustration because, I always have had a feeling, "how in the world can someone develop software for the community for free?", save the gratitute that people show. Everybody, including me, no matter how much they (we) have, always look for money, in return for the work they (we) do. I personally think, Jeffrey should be paid for all the good works he has been doing for Light-Room, either by Adobe, or by the people who use it. But, this feeling is because, he reflects some of my own feelings.

So I set out to find, how in the world, guys like Linus Torvalds, Richard Stallman, et al, get paid. For one it seems that Linus Torvalds works for some company, but I could not find how Stallman is getting paid, but he continues to live :-) ...

The one difference between people like Jeffrey and Stallman, is that, Jeffrey made only the deliverable public, this means, he can be only responsible for maintaining it. As everyone in Software Industry know, the first release is just the beginning, maintenance phase(s) follows. The length of this maintenance phase depends on many factors, but invariably very long. In any case, its too much of a responsibility for an individual, who has personal commitments too. To the contrary, the people in the GNU world, just delivered the source, and deliverables public. This allowed a community to maintain and take things forward.

I am not sure, if Jeffrey will ever make the plugin source public, this may reduce the responsibility that he holds. But if he just wants to make a few bucks to keep up his hobby. Now, I have a problem, I do not have a credit card, and so cannot pay online ;-) ... I will soon try to find a solution to pay him.

What do you guys think about this? Can programmers develop 100% free softwares for the community. Is it just another form social work for the computer geeks (who mostly have enough money) ...