If the disc doesn't have a silk-screened Apple label and logo, then it is pirated. It doesn't really take much analysis.
While reselling burned media on eBay is most certainly a scam, I will say that not ALL uses of OS X from burned DVDs is pirated software.
My employer also has a volume licensing program, with Apple, Microsoft
and a number of other software vendors, including Adobe. The majority of the OSes and software packages we purchase through that agreement come to us as downloadable ISO (after authentication, of course). We can then burn a copy using our own CD or DVD media, and a PDF copy of the software license is also made available for download, complete with serial number. Separately, the
genuine license, on paper, is delivered by mail.
We can also ask to have media shipped to us, but more often than not, we shell out 10 or so extra bucks and end up with a burned DVD, same as if we had burned it locally.
This was the case with Tiger. However, Leopard was a different story, and we did get boxed copies with pressed DVDs in that case (there was no "burn you own disc" option for Leopard).
In this case,
our use of that software on that burned is perfectly legal, and we have the documentation on file to prove it. there may be other large businesses or educational institutions who have similar agreements. Their use of burned media is legit.
That said, we DO get significant discounts for buying in volume and as a result, I do not think it's kosher to resell these licenses, even if we're no longer using them.