From Compsci.ca Wiki
Django allows you to put together multiple applications in a single project. Applications are structured so they are plugable into other projects, so it would be easy to make use of pre-existing applications written for Django to speed up development.
The following projects look like they might be of interest.
Django Forum is a simple forum system.
Django Registration looks like a simple registration system. Users can create accounts, an e-mail is sent to their e-mail address, and they click on the link in order to make the account active.
Other Python Components
If the forum does not have any BBCode parser, the Postmarkup project provides a simple Python module for turning BBCode into XHTML.