When i like a certain Javascript (for menu highlighting or so) used by some website, it would be pretty easy to copy this script from that site's source-code and use it in mine.
I would consider doing so as unauthorized use of intellectual property, since I have been granted the right to use this javascript in my browser, but certainly not to copy it and use it for my own purposes, even though it is so deceptivly easy to reuse other people's work without asking for permission.
I don't know much about online-copyright law, but is my stomach feeling right in this case?