Honestly, i would not see why this would be not legal. They are sounds that where published by apple, and apple dit not forbit any republishing of thoose sounes.
Not sure. But it's true, the voice over sounds are located in a very certain directory on the mac. I copied them from there, but I won't share them here. Only private.
Well, you can also find Windows sounds on your computer and copy them. And Windows sounds are being shared by everyone, but I didn't know that Mac sounds were shared with the public by Apple and this would be legal for any OS.