That extension is stale and doesn't work. There is a better extension that SMF uses on their own Wiki, however it has certain database limitations that open potential security holes. After what happened to the old site, we erred on the side of paranoia and did not go that route. However given the pain in managing the Wiki as it is now, I am looking at it again. We'd need to make changes to get it to work, but it may be the best route for us.