Do realize some facts that are inherited by the nature of FOSS games:
You will never make as much $$ as proprietary games unless your game is proprietary too. For this fact you will lack in support, developers, and other required resources.
While the concept of FOSS is great ([free]dom), it is by nature incompatible with making money (the "free" aspect). You are often left depending on the "good nature" of people to make any income, and that is nowhere near reliable.
All FOSS-business models are vulnerable to competition. Very vulnerable. Consider a MMO game that is FOSS but makes money through the online gaming service. There is nothing stopping someone else--who didn't invest a dime in development--from offering the same service and making money off of your hard work. Heck, they could even offer it for free. All this because you have licensed it saying it was Ok to do. A prime example of this fact is that of Nexuiz/Xonotic: http://xeno.planetxonotic.com/forum/....php?id=150%29
The special exception to this is for large corporations in scenarios such as Andriod, VP8, etc, but are completely worthless for non-multi-billion-dollar-corporate projects (aka: us).