Goodish news, it won't be gone forever. Currently posted on the forum page:
Sorry guys, the Nook is down.
The reason is that we hadn't updated the forum software in time, and spammers injected malicious code which started pumping out over 1000 emails in an hour from our server.
Our host saw that as suspicious behaviour, and shut our email system down. I'm currently downloading the Nook from the server, so I can search through and replace the infected PHP files. The nook forum download is 85% complete after 40 hours downloading, so it will take a while.
The database error message that was here earlier, was because some PHP files have been replaced by virus infected versions. I do have a backup of the forum software, but until I know which files are infected, I don't want to swap things over, as I want to track down the virus, instead of just swapping files around, hoping that overwriting them all fixes it.