Whether to use an open source or proprietory framework:
Having been through the mangle on this, and having seen more and more examples that I felt disinclined to be associated with, I think it has to be the open source all the way.
I think the prime reason for this is continuity – at least you know that what you have today is what you’ll have tomorrow, you won’t have someone changing the rules and/or pulling the plug. The other reason is that if there is a bug/problem, at least you have the opportunity to find and fix that bug.
Is Django up to scratch for large sites:
There’s quite an old blog post here about scaling Disqus to 8 billion hits per month:
Here’s a slightly updated account:
Lists of sites running Django:
I’m pretty sure a web search would throw up options for Python/Django support.