Seconded. Jon Ingold says he’s working on releasing a perl script to help make Undum games, but until something like that happens I think Undum will only be accessible to people who know stuff. (I never wound up doing anything with Firebug and TextWrangler because I don’t really understand what the other people in that thread are talking about.)
[1000T – is it possible to get what you want by setting up wiki software, and then not letting anyone else have an account with editing privileges?]