I don't know where you're coming from with Morpheus being legal but whatever I don't know enough about it to argue.
But to clear things up (everyone seems to be saying that
) Kazaa the program is NOT, I repeat NOT illegal to use. What IS illegal about Kazaa is sharing copyrighted material (music, movies, etc.).
It's this specification that is allowing Kazaa to continue as a company and fend off the lawsuits. Kazaa provides a system to share files. It's up to the users to decide how it's going to be used. It's entirely possible to use Kazaa to share non-copyrighted material legally. For instance I have two Linux distributions in my "Shared Files" folder on Kazaa. When people download those there is NO illegal activity going on. Therefore it is NOT illegal to have the program Kazaa on your computer.
Even though the sharing of the music IS illegal, the RIAA is only going after the BIGGEST offenders. Only keep a maximum of 10-20 files in your shared folder at all times and they will ignore you. This entire suing is just a scare tactic, there's so many holes in their threat and ways to avoid getting sued.