While there is nothing legally wrong with selling a copy of Knoppix, I certainly would never encourage anyone to buy one. In addition to all of the other problems that you have dealing with an amazingly high number of dishonest people on e-bay (non-delivery of the product, excessive shipping charges, and other forms of fraud), you have a serious problem that these people care about maximizing their one time profit, not in supplying a quality disc. As a result the burn is almost always a high speed burn so that they can crank out as many disks in as short a time as posiable. Unfortunately we have seen over and over and over again that high speed burns cause many problems that go away when the disc is burnt slowly. So my advice is to download it yourself and burn it slowly (even if you have to download over dial-up by BitTorrent over several over-night sessions). The price of a CD burner is so low that not having one is no excuse, and you may even be able to buy and have one for as much or less than an e-bay grifter will zing you for a Knoppix CD. Alternately get a friend to download and burn a copy for you, you'll even be doing them a favor if they burn one for themselves at the same time.