The Emacs Wiki is trying to be a multilingual wiki. Benefits, drawbacks, and technical issues are discussed on Meatball, see MeatBall:MultilingualWiki.
This page is for the discussion and implementation particular to the Emacs Wiki only.
You may create pages in any language you want. Pages are encoded in UTF-8.
You can add the main page for your language to the WikiLanguageMenu.
The wiki can have any number of interface languages for the same page database. If you want a user interface in your language (and you are prepared to do some translation work), then all you need to do is this:
If you are used to visit the RecentChanges page of the Wiki every day you might be disturbed by the appearance of many languages. You can always filter the page according to your language by using the URL (in this case english):
http://www.emacswiki.org/cgi-bin/wiki.pl?action=rc&rclang=en
Since the rclang parameter is a regular expression you can use it to access more than one language by using:
http://www.emacswiki.org/cgi-bin/wiki.pl?action=rc&rclang=en%7cde, for example.