I guess it was intended to be a
Subaru engine, and VW sold the rights to it to Subaru, right?

No more than they did to BMW, Citroen, Ferrari, Honda, Preston Tucker, Chevrolet Corvair, Lancia, Toyota.
Karl Benz originated the design in 1898 so ALL other iterations came after that. Almost all
of the later iterations far exceeded the basic design features of that original motor.

Bob