[morgante]

Open Source business models exist, but they are nowhere near lucrative enough to sustain all software developers. Who are you supposed to train or publish books to if every developer is somehow trying to eke out a living in this "open source" world?

[dllthomas]

Well, the above is "business models that could support creating a new project" - in principle one can also eke out a living extending and adapting other people's projects for people willing to pay. Indeed, a huge percentage of programmers currently ekeing out a living programming are already effectively doing that, often in situations where things are proprietary only by default (as in, it's license says you can't share it, but if its license said otherwise it still wouldn't be shared because it's too specific to what one particular company is doing).