> What can be copyrighted are the header files itself: these you can't redistribute, as you can't redistribute the binary that is linked to the executable. Not

> What can be copyrighted are the header files itself: these you can't redistribute, as you can't redistribute the binary that is linked to the executable. Note that while the exact header file is covered by copyright, the "information"/"facts" the header file describes (e.g. said function names, parameters, constants, etc) is not - at least as far as EU is concerned anyway (BTW the case you most likely have in mind wasn't for substituting proprietary parts but for interoperability between parts - i.e. it would still be valid for substituting one proprietary part with another proprietary part). This is also why different compilers for Windows have a "windows.h" (or language equivalent) with each having its own copyright but describing the exact same API. (obviously this is for unsubstitutable fact-like information a header file contains and does not apply for any code like macros or inline methods like in C++ classes/templates)