OpenWiking is the wiki I decided to use for JSForms. It is derived from OpenWiki, old ASP-based wiki.
OpenWiki is written in ASP VBScript and can use different databases (Access, MS SQL, Oracle, etc.) to store wiki. While I would prefer .NET, ASP is much more familiar to me than PHP.
Original OpenWiki was designed to be extensible. It provides facilities to write custom macros to dynamically generate HTML when showing wiki page (table of content for example). It comes with a set of macros and people have written and published more of them.
To show a wiki page OpenWiki generates XML from the wiki text. It is then transformed using XSLT into HTML. This makes it easy to create custom themes and export.
OpenWiki supports hierarchical pages ( in addition to flat list of camel case pages. It makes it possible to create pages with the same name for different parent pages.
The project basically died in 2002. There weren't any updates to it since then and some of the people, including custom macros contributors, decided to revive it. OpenWiking was born.
It's a new generation of OpenWiki. Developers have added more themes and extensions. The project is still in development. While it's not as active as I could have wished, there are occasional updates to it.
OpenWiking lacks some features that I would like to see. There's no normal authentication support. It supports Windows Authentication, but not database-driven log-in. On the bright side it does support page-specific permissions through custom attributes.
I wish there would be more themes, most of them look quite simplistic. This isn't a big problem, since I'm planning to create a custom theme at some point anyway.
Conclusion
OpenWiking is not very popular, but I think it's overlooked. It offers a lot of very nice features. It's stable and has a clear separation between logic and presentation, making it easier to customize and theme.
I looked at the code some and in general it is well-organized and documented.
The wiki lacks several features (normal authentication, discussion for each page, etc.), but most of the important features are present. You can find it on my wiki server.