This is a great thread. I am very curious about this as well.
My preferred model is League of Legends- the game is free and everything that you pay for is something that you can get for free... as long as you're patient, or if you don't mind not having unlimited access to it. For instance, you can play as any of the characters, provided they're one of the several available that particular week. If you're patient enough, you can eventually earn enough points to unlock that character and have access to it all the time. Alternately, you can just pay five bucks for it and be done with it. Sadly, you can't unlock any of their alternate costumes- each one I suppose is a little less than five bucks as well.
At any rate, it's one of the ways you can ride the line of being a developer with a community conscience and a person who is not living on the street. Computers and development time require at least a little nourishment in the way of financials. And we gotta eat, too.
Everybody got to come out of the closet... does that mean I'm allowed to come out of the corner? Is that even funny anymore? Do parents still make their kids stand in corners when they mouth off?? These are the questions that keep me out of the really good schools.