Historically the leading wiki in the Python community is MoinMoin. MoinMoin and the Forest Wiki appear to be very similar. Both are written in Python, provide a hierarchy of wiki pages, page versions, and are customizable. But they are conceptually very different.
MoinMoin is a wiki application based on a list pages stored on the file system or in a table of pages in database. The Forest WIki works at a higher level of abstraction. It is a tree of persistent Python objects, representing multiple content types. Easy to add new content types without making any changes to the database schema. Indeed there is no database schema. GreenMaps.US and UncensoredNews.US have been built on top of the Forest Wiki foundations.
The two products are at different stages in the life cycles. MoinMoin is old mature even antiquated software. It still requires Python 2.7, and does not run on Python 3. MoinMoin's long list of bugs. and feature requests are quite stable. In contrast the forest wiki is just about to be open sourced. It will evolve rapidly. This should be interesting. .
MoinMoin is also quite slow, it loads pages from the file system. In contrast the Forest Wiki can be quite fast. For any reasonably sized wiki, it can and does cache all of the pages in RAM, leading to fast user response. Furthermore the software is designed so that the web server can cache pages for the anonymous user, and only computes pages for logged in users, and the occasional cache refresh.
Hierarchy is dealt with differently. At its core, MoinMoin is a list of wiki pages. When running on a relational database it is a table of wiki pages. Because page names can share substrings, it supports pseudo hierarchies. In contrast, the Forest Wiki is a proper tree of Python objects,accessible by both long url paths, and by canonical urls. The Forest Wiki is a first cousin to Plone. So it is very easy to rearrange the tree, or use its hierarchical security model in large organizations.
The difference is very clear when dealing with larger hierarchies. A basic principal in human factors is that no category should contain more than about 7 items. So the Forest Wiki has very deep, but easy to understand hierarchies. Here is a tree with about 12000 items in it. In contrast MoinMoin handles this list of 486 items mostly as a list. There is a little bit of hierarchy in the list. I tried reading through it, but it really is way way too much for the human brain to make sense of. Rather than being sorted alphabetically it should be a deeper tree of categories.