Yes, Linux is unix.
Yes, we know that Linux doesn't use the original kernel, and isn't part of the Open Group or whatever, but it is the spiritual successor to AT&T's original offering. Linux won. Linux won everything. AIX is dead. Solaris is dead. HPUX (pronounced "H Pukes") is, thankfully, dead. SCO is dead but they'll zombie up every couple of years to sue someone.
Unix won. Thanks to Linux. Do you remember who had the early lead during the Unix Wars? It was Microsoft, with Windows NT. Go back to the late 1990's and hearing about "moving to NT" was as common as hearing about "moving to the cloud" is today. It was Linux that saved us from the dystopia of a Windows monoculture. Not IBM, not Sun, not HP.
Linux has become what Brian Valentine told us Windows would become: "The fabric of standard computing."
The fate that has befallen AIX, Solaris, and HPUX will also strike Windows Server in due time. The writing is on the wall. No one runs Windows Server anymore except to run Microsoft's own server software, and most of that they'd rather have you run on their cloud. Azure networking runs on Linux. Azure Cloud Shell runs on Linux! There is no future for Windows Server, any more than there is a future for AIX. It's merely a matter of time.
God bless the Linux Operating System, the new holder of the Unix crown.