Another thing that would be interesting to learn more about is their Front end structure. From what I can gather they keep things extremely simple (jQuery, mostly) and make extensive use of pjax and server generated javascript that gets evaluated by the client. If this is all there is to it then it is really impressive, considering how many other companies of similar or smaller size quickly inject a Javascript MVC on top of their stack the minute the interaction goes past simple forms (Airbnb comes to mind, who to my knowledge is using Backbone for some aspects of their app).<p>To be clear I think both approaches are excellent and all depends on the in-house talent, but nonetheless it's interesting to see how GitHub is sticking to a traditional, Rails-inspired document-based approach that minimizes front end complexity while other companies do not, even when both have similar UX complexity.