using django and twisted together

Answer 1

I would not combine the two per se; calls into Django would happen synchronously which means that Twisted's event loop would be blocked. Better to treat the Twisted process as a standalone app using Django and to have a classic web server handle the Django app.

You are not likely to find a shared host that will allow you to run a Twisted app, so I would go the VPS route.

Answer 2

If forum application needs to get something from chat application, it's simplier to make forum application communicate with chat application with plain HTTP requests and to make them run separately.

Answer 3

I have a project going that might be just what you are looking for (at least to get started). It is called Hotdot: http://github.com/clemesha/hotdot .

Also, I wrote up more details about this topic here: http://clemesha.org/blog/2009/dec/17/realtime-web-apps-python-django-orbited-twisted/