While the practice of DL from the site while not logged on and then UL while being logged on is not forbidden, I consider it morally dubious. Despicable?
However, you can not distinguish this from seeding things which you have DL elsewhere, and hopefully UL to 1+ in the original torrent (if it was a torrent), so one needs to be a bit careful with blaim... I have done this several times, and I've always taken great care to seed the original DL to more than I got. I cannot see any fault in this, considering basic torrenting principles...