This story says that Telltale is porting their titles to Mac.
-The titles will start coming out for Mac "in a few weeks", demonstration on February 11th at MacWorld Expo
-Buy the title once to get a license for both operating systems
-The games will be released in this order: Tales of Monkey Island will launch first, Sam & Max will launch in several weeks, and the others will be out in the next few months.
-No ports for Bone or Texas Hold 'Em