The gsl is a great resource, but I don't think it suits the author's purpose. He is talking about adding new functions to the C standard library, for anyone to

The gsl is a great resource, but I don't think it suits the author's purpose. He is talking about adding new functions to the C standard library, for anyone to use in commercial or non-commercial software. It isn't practical to stick GPL code into C standard libraries that are meant to be used broadly in commercial as well as free software.