First, people have done similar things in Flash and Java applets before. At the time, both of those technologies allowed for running things inside the browser.

First, people have done similar things in Flash and Java applets before. At the time, both of those technologies allowed for running things inside the browser. Second, I am pretty sure that if someone have done this in another language (Python, Ruby, F#) and provided a platform for easy delivery and sandboxing, the most common response would be "we don't need this, this is stupid".