I made a little bit of money writing open source game.

Some people, like Jason Rohrer, made his living based on donation from the public and patronage. http://libregamewiki.org/Jason_Rohrer

Also, lot of people are probably buying Wesnoth on the iphone judging by tons of iphone reviews that I have spotted using google alert. http://wesnoth.repositoryhosting.com/trac/wesnoth_wesnoth/

Game developers DOES make money while releasing open source software. I just hope you don't move the goalpost in your next comment.