Wildfire Games has decided to switch their development model for their real-time strategy title, 0 A.D., from closed-source to open-source. This 3D real-time strategy game is now having its code licensed under the GNU GPLv2 and the game content is going under the Creative Commons Attribute-Share Alike license.
0 A.D. has been in development for the past eight years, but only now is it being open-sourced in an effort aimed to attract new developers after most of their original team members have since moved onto other endeavors. The 0 A.D. game engine is about 150,000 lines of C++ code and it uses OpenGL for its 3D support along with other common technologies.
More information on the open-source move for 0 A.D. can be found in their original announcement
and their open-source page