Simulation & Toolchain
MuJoCo
A physics engine maintained by Google DeepMind under Apache 2.0 that runs on CPU and is a research default for contact-rich manipulation. Its JAX port, MJX, compiles the physics onto GPU for large-scale parallel training. It is not a either-or with Isaac: MuJoCo for fast iteration, Isaac when you need pixels and sim-to-real transfer.