I'm a bit late to this discussion (sorry) having not been around at all for a while...
Having gone through something slightly similar a couple of times now, albeit just with forums rather than a whole community, I hope I can add something useful.
First - who takes it on?
I'd suggest, based on experience, that it's best handled by a small group rather than one individual. The group can be informal - i.e. there's no point setting up Ltd Companies or partnerships or any of that jive - they just cost extra money for no discernible benefit - do you really want to have to provide a pension, for example, for all the directors of a Ltd Co? It's the law now... I'd recommend 5 people - an odd number so that any controversial decisions aren't tied in a vote; any community should be able to muster 5 volunteers; and it allows for the temporary loss of any one or even two or three members at a time without losing everything. It also prevents one person from "selling out" - a fate suffered by a popular machining forum a few years ago.
The group, once "assembled", sets up the various accounts and services needed to host the community online. I'd suggest, as a minimum, a dedicated virtual server (I'd recommend, from personal experience, Linode. they're very fairly priced, bloody quick, and if the community outgrows the level of server its on, it's a breeze to expand upwards. And it starts at $10/month... End of advertorial

), a PayPal account in the name of the group, and a domain name. Some years ago I grabbed "qluser.org" (with vague plans, copyright permitting, of uploading scans of every QL User/QL World magazine ever published), which I would be happy to donate to the cause. I believe Urs has also offered perpetual use of any subdomains of sinclairql.com, which is very generous & IMHO should be taken up on. 2 domain names = more cost of course, but also provides a handy backup should one of them go missing.
The hard bit, of course, is bringing everything together... all without upsetting anyone. Not easy, but it can be done.
It's been a long while since I've been active on the QL scene (despite owning one since mid 1984, I still have my original QL, although it is sadly non-operational & in bits at the moment, and I managed to break the flying lead which was obviously a Sinclair hardware patch. However, as probably one of the younger QL users - I was just 12 when ours arrived - I'm happy to volunteer to help carry the candle onwards. I've probably got the ability to drag the Wiki over to a new host & fiddle with the URLS, set up forum software if it's decided to move the QL forum onto hosting, etc. The only thing I don't have right now is the financial position to guarantee continuity. Long story short, I'm trying to immigrate my Chinese wife to the UK, which is a long and expensive process. So for at least the next 12-18 months, every penny I have is being spent either on her, or the tax man...
So.. that's my thoughts. Rich - if you haven't already had a better offer, I will volunteer to take over the wiki. I will also volunteer to be one of the group (if a group it is to be), but not it's "leader". I don't do leading. Quite happy to sit in the back room twiddling the keyboards, just don't make me get up there and make speeches.... if you know what I mean.