It was my understanding that UNIX was initially developed by Bell Labs and then thrown out to the computing public for suggestions and add-ins/add-ons. After a suitable time for review of the material added, a "standard" UNIX was presented, while another version was offered by UCSD, and then Linus Torvald offered LINUX, which now comes in many different versions.

From this it may be implied that UNIX and LINUX are growing, developing, OSs which are subject to change as more people become interested in the OS.

Dave