This is a pure Java port of the Bullet physics engine. This port is a modified version of JBullet, which was originally written by Martin Dvorak (jezek2@advel.cz) and may be found here:
This version strips out most dependencies, replacing them with DevilUtil. Importantly, the original JBullet relies on javax.vecmath, licensed under GNU GPL v2, which prohibits proprietary use. This version relies only on libraries under permissive licenses.