This crack only allows you to play through JUST the campaign on the Mac version.
1. Replace the file SC2.app at /StarCraft II/Versions/Base15405/
2. Replace the file Battle.net-patch.MPQ at /StarCraft II/Battle.net/
If you do not see this Battle.net-patch.MPQ file then make sure you have been updated to Base15405 first.
3. Block online connections with Little Snitch OR unplug ethernet/turn Airport off.
All thanks to zeorge_008 and TOBW.