Javascript MVC Frameworks and Server Side Frameworks

I can speak in terms of Rails/Backbone, but I can't imagine that Django would be much different.

First, a client-side MVC framework like Backbone isn't just for single-paged apps. You can also use it to add some rich interaction to one or many views of a more traditional app. They simply provide structure and data abstractions on the client.

Next, these client-side frameworks are designed specifically to work with your back-end MVC frameworks. Backbone.js (since you tagged it specifically) models and collections work with REST services. They will talk via GET/POST/PUT/DELETE verbs and will ultimately communicate with your controllers on the back-end when they make asynchronous requests.

In the case of Backbone, it talks JSON instead of HTML. In the case of Rails, this is really easily handled in the controller. If the request is an HTML one, then you return a view as HTML. If it is a JSON request (*.json or Content-type) then the controller returns a JSON representation of the data. I am assuming that it is as easy in Django as it is in Rails to have the same controller respond to multiple content requests (HTML, XML, JSON, etc)