For anyone who cares, the 'correct' username and password for the Underscore Hosting site are islp4142 and f9dds33, respectively.

Unfortunately this information is entirely useless, as my IP isn't acceptable.

New working theory: doing some portscans, it appears that some of these sites have telnet/ssh enabled. Perhaps with appropriate credentials, such as those of the elusive Beth, we might obtain shell access to a machine that does have an acceptable IP, and might then use telnet or lynx from there to retrieve useful information?

I'm wondering if there actually is a puzzle here. It seems inconceivable that someone would dig a rabbit hole quite this deep...