WoX (MM4/MM5 interlinked) was designed and coded by the NWC team led by Jon van Caneghem. SoX was a fan-designed game, and I'm not sure who coded it. Neither am I sure how much input the NWC team had, although I'm sure that the game had to get the team's general approval. Again, you'd need input from somebody like Timbecile to get those answers.
I reckon it's a bit smaller than MM4, maybe roughly the size of MM3. It ought to be doable in a month, but that depends on how much spare time you have to devote to it, of course. From what I remember, the puzzles aren't all that challenging, so you shouldn't be stuck anywhere for too long.
As a matter of interest, I was never able to complete the game, because no matter which version I used (the original SoX game, or the supposedly debugged version bundled with the MM6 Limited Edition) my game always crashed about 4 moves into the final dungeon.