I am working on a project experimenting with Artificial Intelligence design methodologies for online world avatars. Online world here is quite open to interpretation; Second Life is just as applicable as Counter Strike, for example. To carry out these experiments, I must first develop an intelligent agent for the world in question. However, I am honestly quite stuck as to which game I could use for this.

My preference was to develop an intelligent "bot" to play an MMORPG, but the legal restrictions of such games prevent me. Likewise with most FPS games the use of an intelligent agent in place of a human player is considered cheating.

The alternative, of course, is to create an NPC bot; an intelligent agent that populates the world alongside the player(s) rather than replacing a particular player. However, I'm struggling to find a game that would enable me to create an intelligent opponent either.

I suppose the main requirements would be a game allows a third party program to use the function calls usually utilised by players and read feedback on the state of the world.

Quake III and Unreal Tournament have been suggested before, but they have already been the subject of work on this research project.

Short of writing my own online game from scratch, what games would allow me, through middleware, an API, or otherwise, to create either an artificially intelligent player or a bot?