Some Thoughts on Ownership
There is a difference between what people may call UNIX because of the Copyright ownership on the source code that allows to control what may be done to the source code and the ownership on UNIX trade mark that allows to control who may call a system a UNIX system.
Let me call the first one genetic UNIX wand the second one legal
UNIX.
genetic UNIX
A genetic UNIX is a UNIX that is derived in a direct line from the AT&T UNIX that started 52 years ago in 1969. While some companies may call their product such a genetic UNIX, only two of these companies own the Copyright on that code in a way that they are allowed to control who may see, publish or modify that code.
One company is SCO and SCO used their rights to publish the historic UNIX sources to everyone.
The other company is Sun Microsystems and Sun used their rights to make the modern variant of SYSVr4 open source under the CDDL license. In 2010, Sun has been acquired by Oracle, so that Copyright owner now is Oracle.
Both companies have approx. equal rights on the copyright of that code. SCO of course has no rights on the modern code in SunOS.
legal UNIX
Since the mid 1990s, the trademark UNIX was transferred to The Open Group.
Since 2001, The Open Group also controls the POSIX standard and there is a difference between a pure POSIX system and a UNIX system.
This difference is based on decisions from around 1992, where several entities decided that a pure POSIX system is not sufficient as the base for computers with sufficient usability. These entities e.g. are governmental sites.
If you look at the POSIX standard, you can see what exact difference between a pure POSIX system and a system that may be called UNIX is.
Look e.g. at the definitions for echo
and check for the parts of the standard that are XSI shaded. An operating system that correctly implements all XSI extensions is permitted to be called UNIX if it also passed a related certification by The Open Group.
There is a nice anecdote related to that trademark issue: Apple called their system a UNIX system without having a UNIX conformance certification and was sued by The Open Group to get that certification.
Ken Thompson and Dennis Ritchie originally created the standard in 1969 while working at AT&T Corporation's Bell Laboratories.
– jon.bray.eth Sep 02 '21 at 06:00