Yup! The previous version used JMVC but it was a poor fit. Backbone does juuuust enough to help you out then gets out of your way. Means you have to write a lot of your own architecture but that's pretty much my favorite thing to do ever (and I hated JMVC) so I gladly did so.
The site is way faster now, despite having more stuff going on, just because half the codebase is no longer trying to hack around the parts of JMVC we didn't need.