Do the id game source releases mean that it is okay to download the pak files, wads, and such?
No, the pak files, wads, and such are still available for purchase. The source releases and GPL’ing of the Wolfenstein 3D, Doom, Doom II, Quake, and Quake II engines does not negate purchasing a copy of the game data which contains all the art, sound and map files. A: This goes for the 3D Realms Rise of the Triad, Duke Nukem 3D, and Shadow Warrior source code releases as well as many other games listed in the game list. If a game is in the game list and marked commercial, even though the source is available, that means that the data files still need to be legally obtained.