Libfreenect is not a port of the MS Kinect SDK, it is a low level API that allows for access of the basic Kinect hardware functionality but doesn't support features that the MS Kinect SDK does, like skeletal tracking. OpenNI, on the other hand, is a cross platform library that supports high level features like skeletal tracking, so that would be the way to go if you want to use a cross platform library that let's you take full advantage of the Kinect.
This Python library is a wrapper for the MS Kinect SDK, so it is windows only, specifically Windows 7 only.