traer.physics.js is a JavaScript port of Traer Physics, a Java library originally written for use with Processing. Similarly, the main purpose of traer.physics.js is to be used with Processing.js, although I'm sure you could find a creative use of it to some other end.
Simple, just run build.rb:
$ ruby build.rb
Or, if you'd like a minified version, minified by Closure Compiler:
$ ruby build.rb --minify
That's it! You've now got a JavaScript version of Traer Physics that you can use for your own nefarious purposes.
Rob Hanlon, aka @ohwillie. All original credit is due to Jeff Traer.