After reading about various wiki's (and trying a few) I ended up choosing PmWiki as suggested by Fred.
The new Wiki URL is: http://macromates.com/wiki/pmwiki
It has a link to a static HTML version of the old wiki before the accident including all the textile pages. The textile pages are up-to-date, but the HTML export was done the 12th December, so edits after the 12th of December are not in the HTML version.
I haven't imported the textile pages into PmWiki, since they'd have to be converted, and I'm not sure how easy I can automate this process.
So I'm thinking that maybe I should just leave the static pages and import them manually over time (as they are needed), which also allow for some restructuring of the wiki, which I think was probably overdue (break down most of the big pages and create a better structure).
I'm really terrible sorry about this, and I hope that it's not viewed as lack of appreciation for the many contributors -- I really do appreciate the work that has been put into the wiki!
With this new wiki it also means that I can and will take an active role maintaining the software side of things (which I previously thought I'd outsourced, but let's not point any fingers here... ;) ).
Kind regards Allan