[eluser]jedd[/eluser]
Give me a few more weeks.
Longer response: a while ago I looked around at various auth libraries - and kind of decided on DX - but soon realised that it would require either a lot of munging to make it work with my member and group plans, or it would require me to mung my member and group arrangement. Similarly, I considered trying to rip out the guts from some extant forum software, but without even looking at them concluded that I'd have the same problem, only far more painful as the internals of a forum are less obvious (to me) than the internals of an authentication system.
I think it's a problem that you have already observed, elsewhere on these forums.
I'm not sure what my design goals are at the moment, which makes it harder. I'd like a nicer level of integration than you usually see on web sites with forums - where it's clear that they've tacked on a forum, and haven't even matched the theme to their main site. I'd like to be able to do links in the [ ] style back into other components of my site, make a 'quote' feature for putting into a wiki page rather than a forum-reply, a way of tagging forum threads with keywords that also match wiki tags, and so on. I reason that it'd be as much (if not more) effort to learn and then retro-fit someone else's base product, than to write my own and do it as I go.
Plus, I'm here for the Fun of it - this is not a paid project for someone else. If there was a commercial imperative I'd doubtless approach this differently.
My final observation - apart from some non-trivial logic & algorithm questions on implementation - writing a forum seems to be relatively easy. I say this because I'm not a programmer, or a DBA, or a web designer, and yet I got the skeleton of a forum, using 7 tables, up and going with just a couple of 'real days' of effort. If / when I am not embarrassed by this code I'll happily share it with anyone that wants it - but my gut feel is that, like every other 'drop in library' out there, it will simply be too much effort to wrangle into your extant codebase.