Project Aedra is a free and open-source reimplementation of the engine used in The Elder Scrolls 3: Morrowind. You can check out videos of Project Aedra here:
http://www.youtube.com/user/DragonGeo2
As always, you can download the source code and precompiled binaries for Project Aedra at the main Sourceforge project page here:
https://sourceforge.net/projects/aedra/
Versions of Project Aedra prior to r110 use purely raycasted collision detection without Bullet. Versions r110 and greater use *a modified version of* Bullet Collision and Linear Math.