I was just wondering if the Extreme add-ons to the original Rise of the Triad were Mac compatible, and if so, how to add them on. Any help would be appreciated, thanks.

They are already bundled in GOG's ROTT app. When you start the game, select Setup. In the setup menu, select Use Modified Stuff, select Choose Alternate Game Levels, and select Extreme.rtl. Press space to confirm, go back to the main setup menu and select Save and Run ROTT. You'll have to do this everytime you want to play Extreme ROTT. On a sidenote, see this thread I made about a problem with one of the later levels in Extreme ROTT.
http://www.gog.com/forum/rise_of_the_triad_series/extreme_rott_warning_e4a2

Ah, OK. I haven't gotten to the point where I want to play it yet, but I was curious. Thanks.