The wiki is a fully cloud hosted by Gitbook. The monthly cost is waived for non-profit organizations and open-source projects, so it costs us nothing to host and there's no maintenance required to keep it operating.
The entire wiki is currently synced with a Github Repo under the River City Labs organization. Any changes made there will also be synced back to the site and vice versa.
The preferred method of updating the wiki is through the gitbook web app. See the contributing page for more info.