Faux Pas correctly mentioned that the difference is that someone who borrows a book from a library does not then own a copy of the work. Grishny correctly said that one of the crucial differences is that the borrowed work is not necessarily returned (or deleted) afterward.

The other difference is that the borrowed music file may be listened by multiple people at the same time, which is not legal unless Napster purchased a license from the distributor to allow for that. A library has one copy of the book. It can loan it to one person at a time. One person can read it at a time.

The rules about computer software piracy, since the same person can own multiple computers, and since it is perfectly legal for the owner of a software product to lend it to another, are that it's ok as long as you can *guarantee* that no two people are running two different installations of the software at the same time. Once it starts running on separate computers simultaneously, that's when it becomes piracy.

S "piracy is not quite the same thing as copyright infringement" am