In school, one of my professors had created a 3D game (not just an engine), where all the players were entirely AI-controlled, and it was our assignment to program the AI of a single player. We were basically provided an API to interact with the game world.
Our AI implementations were then dropped into the game together, and we watched as our programs went to battle against each other.
It was like robot soccer, but virtual, with lots of big guns, and no soccer ball.
I'm now looking for anything similar (and open source) to play with. (Preferably in Java, but I'm open to any language.) I'm not looking for a game engine or a framework... I'm looking for a complete game that simply lacks AI code... preferably set up for this kind of exercise. Suggestions?