Yea, you can. Hamachi is compatible with OSX. I can post a little tutorial here in a little bit. But if you want to try it yourself, just google for "hamachi mac".
Hamachi is a VPN client. It tricks your computer into thinking it is LANning with other computers out there in the Internet.
So you can bypass Battle.net using it (and therefore don't have to pay to register Starcraft!). You just make a VPN with the people you want to play with, then play a "LAN" game with them. It's actually faster than using Battle.net, too. (It has less latency)