KDE uses Mediawiki for its wikis at userbase.kde.org, techbase.kde.org, this one and the brazilian team page at br.kde.org This page should give you an idea on how they are set up.
This is not intended to give instructions on how to install Mediawiki, you can find extensive documentation on their site. Here we will explain how it is setup on our KDE servers.
All wikis share a single codebase. The difference comes through a customized Localsettings.php, which loads the config for each wiki depending on the URL that was requested. Those configs are named according to the wiki, e.g. Localsettings.community.php for this one.
Those files only have configuration options which are dependant on the Domain, like the DB that is used or Domain name. Everything else is configured through either LocalSettings.php or CommonSettings.php
There is a certain order in which the configs are loaded:
Our wikis use a custom skin, named Oxygen, which is hosted in svn, see . Lately there is also a new skin in development, called Chihuahua, after the name of the skin from KDE's main site. You can find it in the same repository.