What are some open source AI Bot interfaces? Similar to Pogamut 3 GameBots2004 for custom Unreal Tournament bots or Brood Wars API for Starcraft bots etc.

If you could please post one AI bot interface per answer (make sure to provide a link) and give a brief summary as to the content of the blog posts.

Please include what type of bot interface structure it is, client/server, server/server, etc

e.g. BWAPI is client/server which emulates a real player