Comment by nchapman

Thanks! It's Backbone.js on the front-end (with lots of help from the amazing strophe.js), Rails for the REST API, node.js for lots of supporting services, ejabberd for XMPP, and MySQL for storage. It's one of those problems that seemed like it was going to be simple to solve and then wasn't (as usual) so there are quite a few moving parts to bring the whole experience together.