No, I don’t think django is overkill for a CMS, particularly if you’re already running python and/or are familiar with it.

I’m a little confused about your question, though—are you developing a rich client? Just embedding flash on a page?

As far as a Django ‘call’, I’m not sure what you mean either—if you’re looking to render the html up in your flash client, you can just call whatever AS URL API there is.

Having written Flash clients, though, I don’t really see any justifying reason to have one, but that’s beside the point.