UNIX was originally a registered trademark of AT&T for the Unix operating system. It is now controlled by The Open Group. This is why you might see some people refer to the free systems (such as Linux, and the *BSDs) as "Unix-like", "*nix", "Un*x" or sometimes "unixoid" -- they are not officially licensed to use the UNIX® registered trademark.
See Unix.
41 pages link to UNIX:
