Actually, it's a Backbone.js application. It uses the browserify library to load other modules, which is what the "require('blah')" bits are. this confused me too when I first read it. so essentially you can run this on a static file server like GH pages.

As far as I remember in order to get the GitHub authentication piece working you need to use an external app simply for the authentication with GitHub. DevelopmentSeed also wrote an app for this called gatekeeper (I think) which I believe is a node.js application.

impressive stuff.