Given the explosion of open source released projects I've seen over the past six months, I believe developers are getting compensated by the tool they are building for themselves creating real value for them.

I have a problem, I spend a few days building a tool that solves the problem, it works pretty well for me, and I release it to let others get value from it. They make tweaks to it, perhaps improve it, and I get value from those enhancements and bugfixes.