If the network isn't secure then his computer may well end up on it unintentionally anyway. See my thread nearby.
I wouldn't say there's much to worry about, although I would suggest he avoids his computer having a network name which identifies him personally, as a knock at the door from someone wanting to know why he's freeloading from their connection may be somewhat embarrassing.
Best if he doesn't consider it a long term solution but as a stop gap measure, well, who's to say he even knows it's happening?
