WebJunkie: What legal reasons? So GOG is OK to sell VIOLENT games where you can KILL people but it's not OK to show NUDITY?
In case it hasn't occurred to you, in many countries, particularly the US, nudity is very problematic, especially full frontal and the depiction of genitals, far more than violence. European countries are far more tolerant in this respect but still have a problem with genitals shown in a sexual context which can result in those products being considered pornographic which results in all sorts of limitations on the distribution.
WebJunkie: Oh wait, Lula isn't censored so what possible legal reasons didn't apply to that one?
Because you don't see genitals there (nor semen, I believe). You see both in the uncensored version of HuniePop. Lula is a game ABOUT pornography but not pornography itself. The uncensored version of HuniePop is cartoon pornography.