From my understanding, ur trying to play these mods on a (possibly) unsupported game.. But i may b wrong... IF it was purchased in the steam store, and added to ur library AFTER purchase from steam store, then it might work... But i may have a work around...U said u got ur copy from the App Store on mac... Is there a CD/Activation Key included with the copy u have? If so, remove game from steam library IF u added it by clicking add a game > add a non-steam game button(s). Then if u have CD/Activation Key, go to ADD A GAME... > Activate a Product on Steam and see if that works... BUT u must have CD/Activation Key... Hope this helps u...