&gt;POSIX is not SCO UNIX (UNIX(tm) is effectively a trademark and nothing more at this point)<p>UNIX is more than just a trademark, more importantly it is the test suite you have to pass to be allowed to use the trademark. And the trademark doesn&#x27;t belong to SCO, it belongs to The Open Group, a not-for-profit industry consortium (successor to X&#x2F;Open and the Open Software Foundation.)<p>Does it matter that much? I&#x27;m sure it makes it easier to port a package to a certified UNIX, since you know a certain collection of APIs must be there (putting aside the fact that some parts of the UNIX standard are optional)