(from Can GNU ever be Unix? by Jem Matzan, NewsForge)
Since you don’t need any of the original AT&T Unix source code to certify your operating system and use the Unix trademark, you do not have to license anything from the SCO Group to call your operating system Unix. As a matter of fact, SCO has to pay The Open Group to use the Unix and UnixWare trademarks, and The Open Group is not very happy with SCO’s obnoxious and unprofessional public behavior.
SCO only has the right to license the Unix source code that they have control over; basically what they bought from Novell, which was sold to them first by AT&T. SCO does not control the patents to the Unix source — those also remain with Novell — and whether or not SCO controls the copyright to the code is currently a matter of debate; SCO says it controls the copyright and Novell claims that it still retains those rights. Either way, the SCO Group actually controls very little so-called “intellectual property” with regard to the Unix operating system.
Another interesting SCO-related point is the company’s claim that Linux contains code similar to bits found in SVR4 Unix. GNU/Linux and the BSDs strive for standards compliance on many levels, and that means following the prescribed Open Group, ISO, and IEEE standards as much as possible. SCO has shown little proof of copyright infringement thus far, but has claimed that some Linux files, such as ctype.h and errno.h, are “copied” from its proprietary code. In reality, the similarity is likely due to the fact that in both SVR4 and Linux these files were designed according to published standards. SCO does not own the standard or the material in the standard; it is either trying to intentionally mislead people to give the appearance of credibility, or was not thorough enough in its research on the matter.