Well, some libraries can be really hick-ish. I live in Memphis (a few million people) and the library near me only RECENTLY (like, within the past 5 years, maybe sooner) got not only more than one computer not for reference, but computers that had internet access... You'd be surprised!
But let's think about some things from a busy lurker's P.O.V. under the assumption Brother IS in fact a double-agent (I read it somewhere; it's SO not my theory)...
What if Brother is currently at Op's facilities? Maybe helped Tach break in or sumthin? What if Tach decided to take the blame to enable Mister Billeh-Bob to continue his work there? It's guessing, but not too much of a streach.
If Brother Billeh-Bob is a double-agent in Op's facilities, the code makes PERFECT SENSE!
~ A library is where you get information, and BB & T are trying to get info from Op!
~ One computer would make sense in something like a small security room
* but with someone already there, he couldn't do his regular work when he intended to and had to wait till the coast was clear
~ an AOL disk is a program, so what if he was trying to do a phising-type virus/program in Op's databases? All the movies show that viruses are very efficient when put directly into the intended computer...
* But Op's system is better than he thought, thus the story about an "any key"; the security measures got him so turned around that he felt like a complete idiot
Thank you Attention Deficet Disorder for helping make this theory!!

LOL
Btw, I'm mainly a lurker. I work 18 hours a week and take 12 hours a week worth of classes (including Japanese) so I can't participate in code-breaking.

Sorry. But perhaps I can contribute like this in looking for new theories based on given info! ::hopes she can be of SOME help::