X Windows

But that's nonsense. Microsoft would never have the shadow of a hope of winning such a case,
and they know it, so they would never ever even seriously consider even filing it.

Imagine the headlines: "Microsoft loses the rights to Windows!"

Thing is, such a GUI is known as a windowing-system, and was long BEFORE Microsoft published
any such GUI. When they did, they named it "Microsoft Windows", because that was the ALREADY
ESTABLISHED terminology.

The screen can contain many 'windows', each program runs in its own separate 'window', those
are the generic terms.