Pcwiki
From ProgClub
Pcwiki is the ProgClub Wiki software. That's the software that drives the web-site you're looking at. It's a fork of MediaWiki 1.17.0, with a custom theme called OldSkool, and the NoTitle extension. Pcwiki has also been updated to include a link to the W3C HTML validation service at the bottom of every page, boasting HTML5 support.
The code for pcwiki is publicly available from svn:
http://www.progclub.org/svnro/pcrepo/pcwiki/trunk
Or privately available for read-write access:
https://www.progclub.org/svn/pcrepo/pcwiki/trunk