It's strange, I have been running in circles in my head at how to respond to this thread. I am in a weird position that I probably have time in my schedule to assist in the development of a website, but likely no time to maintain or support it.
In other words, I always have times to give my opinion!
My first opinion would be to look at using a content management platform like Drupal or Joomla... but that requires a LOT of maintenance. They are nice in that they are a web page version of an Operating System (for lack of a better explanation) that lets you install plug-ins on the web page to do a million different things.. from blogging to forums to store fronts.
They are hugely flexible, but probably not always the most intuitive. I've worked with Joomla, mostly, and there is a lot of work involved in building the framework of a web page, but once it is built the only issue becomes patching and updates which, on occasion, have a way to break all those plug-ins.
The other option is something more straight forward like Wordpress, though I've not looked at wordpress all that much and not sure whether or not it supports forums.
I think the biggest headache, should you choose to accept it, is finding someone who has the time and know-how to port all the content of the current forum into a new forum software (1-2-3 NOT IT!!).
If I get some time this week I'll throw a few options up on my test server (namely Joomla, Drupal and Wordpress) and send you the links and the logins and let you poke around in them. It's been a few years since I got too deep into my web dev hobby, so if I find something along the way that might suit you better I'll host that too.
None of it will be given a Dan Simmons wind dressing.. except maybe an image in a test article to test the functionality.
This is entirely free of charge, by the way, since you've been such a gracious host over the years. And I'm not certain how much use you'll get out of it, in the end.