Jiglibflash is a as3 open source 3D physics engine with a MIT license (ported from c++ Jiglib).
Supported 3D engines are: Away 3D, Away 3D lite, Five 3D, Sandy 3D and Papervision 3D.
The source and examples can be found in the trunk at the SVN (see source tab). There's a flash 9 and flash 10 version.
There is no documentation yet, but you can find a short tutorial in the Wiki.
You can reach our blog at: www.jiglibflash.com/blog.