The wiki is English because the server is English.
The mod is released with English documentation, and all in-game text is English. The wiki starts as better documentation for the mod as it is distributed, then when there is a difference between the client files and what has been changed server-side, the server-side information (from the GC 24/7 server only) is used instead.
Those are the primary reasons why we've made no effort to translate the wiki. The other concern, which has already been brought up here, is that the admins already have troubles with people who can't speak English trying to play on the GC server, and providing documentation or even just the rules in another language would only encourage it.
<lurk mode re-engaged>
Some say that he's a CIA experiment that went wrong, and that he only eats cheese. All we know is that he's not The Stig - he's The Stig's American cousin. Wiki sysop (admin-ish) | I do custom ship renders (and bases)