[msclrhd]

And the nightmare of determining who owns the APIs in things like SQL, BSD, POSIX, libc, speadsheet functions, the cairo and HTML canvas path APIs, HTML DOM, and more. Not to mention compatibility projects like wine, DOSBox, and various emulators. If printf is copyrighted, it will affect C, PHP, python, the command line application, and others. Then there are things like where C# is clearly influenced by Java.

The whole programming landscape would need to be audited.

[pjmlp]

A large majority of those APIs are protected by ISO, ECMA, OpenGroup with their respective copyrights and many of them aren't available for free, specially ISO ones.

You just them as free beer, because a couple of developers have decided to put their money for you, specially the ISO ones.