You could use it to scan the UPCs on your books or CDs or DVDs to create a catalog of your media; you could use it to scan UPCs on your groceries to make a shopping list. You could do any and every one of these things, because the Cuecat was yours.
Cuecat's manufacturer, Digital Convergence, did *not* like this *at all*. They sent out legal demand letters and even shut down some of the repositories that were hosting alternative Cuecat firmware.
6/
They changed the license agreement that came with the Cuecat software CD to prohibit reverse-engineering.
http://www.cexx.org/cuecat.htm
It didn't matter, both as a practical matter and as a matter of law. As a practical matter, the (ahem) cat was out of the bag: there were so many web-hosting companies back then, and people mirrored the code to so many of them, the company would have its hands full chasing them all down and intimidating them into removing the code.
7/