Are there any open source AI subsystems one can use in own game engine?

I know there are free and open sourced scene graph libraries (or subsystems) that one can use in own 3d game engine. There are also physics libraries, particle generators, but whatabout Artificial Intelligence? Are there any such open source projects/libraries that could be used in a development of one;s own game engine(supporting nn, fuzzy logic, state machines etc…)?
Huge thanks as always,

AI is a very complex subject. there is no AI library (AFAIK) because each application needs different behavior.
for FPS games, AI does path finding + team/solo fight. that could be simple but each FPS is different. quake3 bots don’t react like unreal bots or military simulation bots.
for strategy games, it is the same.

each game have its own AI because each game is unique.

maybe I’m wrong, but that’s what I feel when I play games.