Wine tells me otherwise from reimplementations.

Also, https://osgameclones.com

Otter Browser it's pretty much inspired from Opera 12 too.

And, for a much better example, XMMS vs WinAMP 2/3, virtually the exact same interface, with skins support.

GNU/Linux itself clones the Unix interface, API and ABI. And so did the BSD's.

Another example, Lesstif when Motif was propietary. Same API, and you could run lots of stuff written for Motif under LessTif. Now libre Motif superseded it around a decade ago.

What the music and movie industry did and does, in regards to IP, is the counter-example.