I mean kind of in the way that you're visiting someone's house and they play some music. Not that you get a copy of the music for yourself. I guess iTunes does something like that but isn't it only limited to a local area network? Halp. :-\
Yes you can share with iTunes up to 5 computers. I have 3 right now with my iTunes account. Also you can delete computers and put others on the network so it works out well.