Some art that are used in AoP come from Fallout, Fallout 2 and Fallout Tactics. That mean that in order to have the right to use those art, you have to buy those 3 games.
If you don't, then somewhere, some people may become angry.
On another hand, to be able to launch AoP, you only need 2 files from Falout 2 (Master.dat and Critter.dat).