Weird thing, Lucas and Carla were invisible to me too in the sex scene. But this is possibly a glitch, because the GOG version is uncensored, no doubt, and also 'cause the censored version doesn't remove the nude models.

They have no policy related to censorship at all. We only have the uncensored version because it's the European version of the game and the latest official patch doesn't take the nudity out. If they didn't sell censored games, then why do you have to mod Fallout 1 to enable kids?