It is. I tried it out but it doesn't have the fidelity w.r.t I/O and 'hooks' I was looking for. Then again, I'm working beyond reinforcement learning. More advanced A.I necessitates more advanced gym.

I highlighted box2d as its an opensource physics/sim engine.

The sim/physics engine is 90% of the 'gym'. I'm sure if there was money involved, the sims/hooks/etc that are being sourced and packaged around could get a lot more advanced more quickly. i.e : https://github.com/erincatto/Box2D/issues