Setting up restricted accounts for Libraries

I have a WP site with databases accessible to registered users of the site. I use s2member to restrict parts of the databases to paid members of the organization (a genealogy society). There are libraries interested in subscribing to the databases, so I want to set up user accounts for the libraries, which might have the databases accessible from let’s say 5 computers at once.

Ideally what I’d like is one account that can be used on those 5 machines, and not used anywhere else (i.e. if someone has the username and password and puts it on their own computer, it won’t work, or if they use it outside the library, it won’t work.

s2member can partially handle this in that it can restrict how many different IP addresses can be used a month by a specific user. That’s helpful, but not foolproof.

I was hoping someone had suggestions for options on how to deal with this issue. Does anyone else offer Library subscriptions to their site?

Thanks.