Sputnik

Sputnik is a wiki written in Lua. It is also a platform for building a range of wiki-like
applications, drawing on Lua's strengths as an extension language.

Out of the box Sputnik behaves like a wiki with all the standard wiki features: editable
pages, protection against spam bots, history view of pages, diff, preview, per-page-RSS feed
for site changes. (See http://sputnik.freewisdom.org/en/Features for more details.)

At the same time, Sputnik is designed to be used as a platform for a wide range of "social
software" applications. A simple change of templates and perhaps a few spoons of Lua code can
turn it into a photo album, a blog, a calendar, a mailing list viewer, or almost anything else.
So, you can think of it as a web framework of sorts. In addition to allowing you to add custom
bells and whistles to a wiki, Sputnik provides a good foundation for anything that's kind of
like a wiki but not quite. Sputnik stores its data as versioned "pages" that can be editable
through the web (just like any wiki). However, it allows those pages to store any data that
can be saved as text (prose, comma-separated values, lists of named parameters, Lua tables,
mbox-formatted messages, XML, etc.) While by default the page is displayed as if it carried
Markdown-formatted text, the way the page is viewed (or edited, or saved, etc.) can be
overriden on a per-page basis by over-riding or adding "actions".