This is why I don't understand copyright law. Aren't data facts? Facts can't be copyrighted, right? Where a business is located is a fact. How can they say how someone else can use that fact?
By signing up, you are making a contract with geoapi. If you violate that agreement, then they'd (potentially) have a case for breach of contract.
http://en.wikipedia.org/wiki/Feist_Publications_v._Rural_Tel...
It gets hairy though because you are agreeing to their terms of use in return for the API key, and I'm not sure how that factors in. They're well within their rights to refuse service to you, but if you were able to scrape their data without agreeing to their terms, it may be legal.
Of course there's a million other places to get this data, and I'm not suggesting you scrape theirs. But I don't think there's anything stopping you legally, just some FUD in their TOS.
Would be very curious to hear from the site owners on this topic.