Differences I noticed: in my system a page implements a module instead of a function. Code, evaluations, and commentary are mixed in a literate-programming style. Anyone can edit existing code, with a branching version control system for backup (which, er, I never hooked the UI into). It's awfully hacky. Maybe some of these ideas could influence this newer wiki, though.
I'm not the original poster, but MoinMoin is widely considered mature and featureful. I'm guessing they had a good reason not to use it; it may be worth asking them.
MediaWiki has been extended a whole lot for dynamic content in Wikipedia. That might be one reason for the author choosing it. There has been work outside Wikipedia in making content features more powerful, with Semantic Mediawiki and DBpedia.
I'd rather have Wikimedia in PHP that works than use a half baked solution because it's written in python. Languages are tools -- elitism not necessary here.
Looks like the site is down -- I couldn't seem to find a cached version anywhere. Here's a discussion on reddit about PyPedia from six months ago posted by the creator of PyPedia:
An example of what I wanted to do with it: http://wry.me:8080/page/Partial%20Evaluation (Only the early bits are working.)
Its own source as wiki pages: http://wry.me:8080/page/Underlying%20Source%20Code
Differences I noticed: in my system a page implements a module instead of a function. Code, evaluations, and commentary are mixed in a literate-programming style. Anyone can edit existing code, with a branching version control system for backup (which, er, I never hooked the UI into). It's awfully hacky. Maybe some of these ideas could influence this newer wiki, though.
(Edit: fixed links, added differences.)