This is a clone of a box2d javascript engine which is a clone of the box2d C++ library.PixelLab modified the library to use Google's Closure Javascript Compiler for great compression--with the added benefit of compile-time checking. (We found a lot of bugs in the original javascript).It's being used in Agent 8 Ball, an HTML5 showcase pool game.Check out the source, fork, patch, etc on Github.