I just looked at the source, and… well, none of the NxRevoluteJoint methods are wrapped. Same for most other joint types. It wouldn’t be hard to add these methods, just apply the same pattern as found in other objects. NxPanda is far away from being complete, I know.
By the way: casting is something you can do in C++ and some other languages, but not in Python. And I think this is a good thing.
(Almost) all NxPanda objects are created using factory methods, which take an descriptor object as argument. So I have explicitly disallowed to create the Python wrapper objects for these classes.
enn0x