Wildfire Games has announced that it will be moving its previously closed development process for 0 A.D. to open source. All code will be released under the GPL and all art under CC-BY-SA. 0 A.D. is a historically-based RTS, and while it's not yet complete, this trailer is purportedly actual gameplay footage. With a codebase of over 150k lines of C++ code plus 25k lines in development tools, this is looking like a fairly promising entrant into the open source RTS field. The screenshots are definitely pretty, to say the least.

http://games.slashdot.org/story/09/0...es-Open-Source