ZDNet has an article on “Altruism and open source“, in which the relationship of open source success and altruism is discussed.
Personally, I’m not sure Altruism has anything to do with why developers choose to participate in open source projects.
As ESR pointed out in The Cathedral & The Bazaar, the reasons for developer involvement in OSS projects are often internally focused. Things like, recognition of peers, having a need for the resulting software, etc.
I’ve likened this to the idea of a Capital Equation that, when balanced in your favour, you’re happy to contribute to the community, answer forum questions, fix bugs etc. However, when the capital you expend on the OSS project is outweighed by the capital you receive back (i.e. from recognition, savings vs. going out and buying a commercial product, etc), then you’re going to want to tip the capital equation back in your favour again…and well, go get a job that pays you to work on the project full-time. The other alternative is to work less on the project, to the point that you’re not expending more capital than you are receiving. This happened with Linux developers, and with JBoss as the article points out.