[shwouchk]

What about the concept of a window? Can anyone own that? Or, a cat octopus? How about a discarded piece of fruit?

[richbell]

There is nothing distinct about a window or piece of fruit. Obviously if you made an operating system called Windows and used a window as a logo that would be trademark violation, but there's nothing stopping me from opening John's Windows with the logo being a window.

[shwouchk]

Sure, a trivial strawman example.

But then, if you made not an OS but rather say, a search engine called “pane.io” and used a logo of a 4 pane window of different colors ?

I am open to being wrong here but I doubt it would have gone smoothly.