There is an open-source game that supports AI making with a complete interface and has a few fairly well-developed AIs with source available for reference. The difference from say, ORTS is that it is a LOT more complex in pretty much every aspect, thus if you can make a good AI here, any other RTS should be a doddle. AIs are packed as DLLs and can be freely distributed to anyone who has the game. The game engine is called spring, with a few hundred users always playing it at any given time with a variety of games. Take a look at some of those screens! http://taspring.clan-sy.com/ <- main site http://taspring.clan-sy.com/phpbb/viewforum.php?f=15&sid=70e5c22a3aa49067f7af5424b4bb4b56 <- AI forum