Generally speaking we haven't had much need in formally defining a rules page for the wiki. The main point of this page is to help encourage people to contribute by telling them that it's okay to do various things, but in time this page might evolve into more than that.
Who can edit?
Anyone! Users, XBMC developers, companies, organizations, add-on authors, you name it. As long as your contributions to the wiki is reasonably objective and related to XBMC, we most likely will welcome that information. Of course, there may be exceptions to this from time to time, but don't worry, we'll politely let you know if anything is ever an issue, and you won't get banned for simply making a mistake.
What other rules apply?
The XBMC Forum rules basically all apply to the wiki as well, especially regarding the Piracy Policy.