Also
Pyjamas: http://pyjs.org/
Skulpt: http://www.skulpt.org/
and another one I forgot.
They are all are cool projects. They diligently solve 73.56% of the problem of Python to Javascript translation, and the other 26.44% remains a very hard task. This is not unlike many other problems in programming (well, even in real life). So it is not for the lack of knowledge, experience or hard work, it is just a very hard problem.