More than likely this and many other films that have never been made available to the public are being dubbed onto DVD or videotape from a television broadcast. The ethics of selling these is quite debatable, and has been an issue since the early 70's when cassette tapes and recording decks were first sold and enabled everyone to copy their friends' record albums onto tape and "own" them.
My take has always been, why go after the consumer? The technology has been manufactured and marketed by Sony and a thousand other electronics firms for the obvious purpose of copying, with some kind of bogus disclaimer about copying your home movies or some such b.s.
And has been stressed by other posters, all these great movies that true film buffs are dying to see are not being released because the market is not large enough, and I for one will buy unauthorized copies to view these works of art. If that makes me a "pirate" or a "pirate's enabler" then so be it.