I don't know but I accessed it through a mod that was released within two days of the game's release. I imagine the construction kit was used since there were plenty of mod makers wanting to get their hands on the game.
It really isn't a mod. All you do is remove the art file that contains the "upper clothing" for the female characters (Essentially the leather bra that appears on their chest when not wearing any armor) and you've successfully boobi-fied your game.
It isn't even very well done either. The textures weren't finished and four small white marks are "tattoo'ed" onto the sides of their breasts. Looks weird, to tell you the truth.
Then again, we are talking about polygons here.
EDIT:
Also, I remember Gothic 1 having a servant who bathed in the Old Camp leader's personal room, and if you removed a certain texture file her clothing was not there the enxt time you went into said room. This caused a bit of controversy amongst the fan base of the game (Back when it was new and only nerds like me were playing), but they never changed the rating.
This comment was edited on May 3, 19:55.