Wow... according to Wikipedia, the women on the box were all employees of On-Line Systems, the precursor to Sierra. One of them is a bookkeeper! I'd be curious as to how the convinced them to pose naked on the box.
The Digital Antiquarian wrote some interesting blog posts on On-Line Systems and Softporn back in February (with screenshots!). This blog is a great read for info on this and other early adventure games and their creators.
Steven Levy's book Hackers from the early 80s has a large section on On-Line Systems including the story of that photo. On-Line was a party, that's for sure.