http://www.syntensity.com/
Some guys have taken the cube2 code and modify it to be a script and modding heaven using Google v8 java engine and other stuff
So if some have a modding urge or a more general "I want a 3d game engine that does all of the stuff nowa!!" check it out
All open source
Now in current beta/alpha(not really sure) but the code-base is pretty stable