One of the differences between Django and Rails is that the former makes almost no assumptions about how you are going to write your front end. I don't know much about Rails, but it seems to me that it is much more opinionated in that regard.

Re: Django & Backbone, you should check out djangbone. It makes it dead simple to create a basic backbone-compatible APIs in Django, and is easy to extend if you need more advanced functionality (full disclosure- I'm its author): https://github.com/af/djangbone