We had a lot of reasons we wanted to build our own help desk, the least of which (and easiest to mention) is that a three seat license to the top tier desk systems are well over $100/mo. Plus they were slowing us down quite a bit.
Right now its only dependency is Django, it supports email alert for updates, has bundled style, a permission like public/private/internal status, optional anonymous questions/responses, categories, searching, and a few more I've missed.
What I'd like to do is: extend tests, class based views, parse incoming emails as questions & response (this is important for help desks), better mod tools and internationalization.
Anyways, see the GitHub repo: https://github.com/zapier/django-knowledge, the docs: http://django-knowledge.readthedocs.org/en/latest/index.html or check out a live demo at Zapier: https://zapier.com/support/
We've also registered django-knowledge.org. If anyone has thoughts on a good, cheap lightweight host, let me know.