While Windows has some Unix influences, it is not derived or based on Unix. At some points is has contained a small amount of BSD code but the majority of its design came from other operating systems.

Is Windows made from Linux?

Since then, Microsoft has been drawing Windows and Linux ever closer. With WSL 2, Microsoft started including within Windows Insiders releases its own in-house, custom-built Linux kernel to underpin WSL. In other words, Microsoft is now shipping its own Linux kernel, which works hand-in-glove with Windows.

Which OS is not based on Unix?

So what is the answer? If you confine your frame of reference to #6, then Windows is indeed the major non-Unix (though it is POSIX-compliant) operating system out there.