Imagine if Xerox or their IP purchaser, Apple, tried to put out a retrospective IP Inovation claim for WIMPs.
Atari
Amiga
x86 Windows
X11
Linux and Open GUIs
Even c64 GEOs
Would all be potential targets.
But as Apple already make "passive" claim for the first "true" Personal Computer: The Apple (Apple 1 is the retrospective naming), the above is possibly moot.
BTW: it was released on "April 1st" 1976. (And we're still waiting for the punchline from Job's?)
As it was, the Apple(1) was a Kit so from an innovation perspective of a usable Personal Computer product they miss the IP boat. Back then such devices were called "Micro Computers"
It was the Commodore Pet in 1977 that was the first complete (Keyboard, base unit, monitor) micro computer for the public consumer. It was produced and marketed as a PC. Closely followed by the Apple II.
So who actualy owns the Commodore name and the IP potential to the inovation of an actual marketed product that includes a Monitor, baseunit and keyboard for personal use.?
Of course the final logical step in this possible line of legal precedent would be Charles Babbage's decendents claim.
It's a never ending story.