I think there's an important distinction to be made between unauthorized, potentially out-of-date and not necessarily well-supported mirrors of an active piece of IP and the preservation of a useful resource which has only gone missing because somebody's interests have changed and their old website went down. In the past we've repopulated old TeamBG tutorials which were lost to site disappearances and we would certainly do it again if need be, knowing full well that if the authors resurfaced they'd be welcome to ask us to take it down blah blah etc.
(Bottom line: it's good that SP has them up. If they hadn't, I'd have plucked them from Google cache/archive.org and put them somewhere myself until such time as Xyx and UU showed up again.)