If you're interested in node, I highly recommend poking around the source files. Pretty amazing what's possible in a small amount of code.

While the frontend is all Backbone, the real magic happens in its backend dependencies like peerflix (https://github.com/mafintosh/peerflix) and video.js (https://github.com/videojs/video.js/).

Edit: And, of course, the remarkable (undocumented?) API provided by subapi.com. Check out http://subapi.com/popular.json !

Double Edit: The API appears to be developed by the Popcorn Time people, as per https://github.com/popcorn-time/popcorn-app/issues/294