In this subthread, we were discussing "the interface something is not copyrightable as the law says today, but the description of said interfaces may in fact be". The header file was an example of how this is already generally assumed to be the status quo - the API is not copyrighted, but the particular description of that API, in form of <windows.h> that ships with MSVC, is copyrighted. So MinGW could do this for Win32 API, so long as they rolled their own header.