Quote:
Linux is a UNIX-Like Operating System, written from Scratch, based on the POSIX Standard, that defines the Way a UNIX-Like OS must work.
All Unixes must be POSIX Compliant, no matter if it's Linux, BSD-s, HP-UX, AIX, Solaris, IRIX, etc, etc....
After All, UNIX is a Trademark that originally belonged to Bell Laboratories (AT&T), and has been sold to one company to another with the years... (UNIX is what the owner wants it to be)
So, POSIX is the Standard, but for Tradition, all this POSIX-Compliant Operating Systems are called UNIXES, or UNIX-Like.