i think he meant that it is legal to do so but not a feature of iTunes.
the "sharing" feature in iTunes right now can not share music bought from the store, OR ripped songs, you can only stream, but you can not copy over, BUT it is certainly not ILLEGAL to copy the songs to another computer!
I frequently do what you are asking via iChat and Rendezous just sign both computers on (i don't even think you need to have an AIM/.Mac account name) and send that way, simple as cake, or you can do like they said and share it in the folder OR you can connect to the other machine via NETWORK and get it that way