We cannot afford being cut-out of this!
Yet we have to deal with resource limitations, most notably a chronic lack of time.
You may get the source code https://github.com/kripken/emscripten/wiki and read about it from http://syntensity.blogspot.com/2011/04/emscripten-10.html (in http://syntensity.blogspot.com/ ), a blog continued in http://mozakai.blogspot.com/
Actually there are some enjoyable considerations about how such a tool shall be called:
Q. Is this really a compiler? Isn't it better described as a translator?