I think that RWS still holds rights for title. So you can't start your own commercial project as spin-off of commercial title Postal. Also, you want to place your game on PIII story which one is property of Akella. That's what I think. I could be wrong. I don't know.
EDIT: How many ppl are working or contributing on this project?
EDIT2: Have you already done something except story, info and ideas?
EDIT3: That main designer is from Russia.