Probably Galahad will know this one, but if I had to hazard a guess, I would say it is a stolen pre-release. On the BBS's back then, very often you would see the same getting uploaded from a different crack group and the -=* SALES VERSION *=- or something like that in the description, so it wasn't exactly an uncommon practice. Thing is, most users destroyed their previous copies, making those harder to find. The ones that are still around today missed the chopping block (which, to me, is a good thing!)
I'll check some of my old lists of BBS uploads and see if I can find this one and report my findings (if any)...
Edit: I checked the text lists I have on my PC HD here and could only find the upload for the Anthrox release of the game, which didn't mention anything like that.