It's called "ZWiki" and it runs on Zope. You can find the ZWiki stuff at www.zwiki.org and Zope at www.zope.org. It was really easy to set up, and of course if you're already using something Python-based, you'll be happy to know that Zope is written in Python. (I personally can't get into Python, but that doesn't mean I can't use it and like it. :)