So it turns out you CAN earn money on non-copyrighted work. $40,000 is not a small amount for most people. Well-deserved for the developer, hats off for the idea, implementation, and Bitcoin as a payment option.
A bit OT but what are some of the most successful open source game titles out there? I'm writing a game server backend right now and didn't find very many projects where I could read good quality game code. (I come from the JS web app world where everything is out in the open so I'm super biased)
I found Battle for Wesnoth to be entertaining as a game. It's open source, but I don't know about code quality. If you are willing to read code from when dinosaurs roamed the land and sea, try Nethack.
If you only care about reading code, open source or not, I think the first Deus Ex's in game scripting code was visible in the game's editor. (And the rest was the first Unreal engine, whose might also be available for reading nowadays. Or you just read the source of the various Quakes.)