Gnu can be used to describe the gnu project, the gnu license or the gnu coreutils. In this context, they mean that Linux by itself isn’t enough to be the a free desktop, and needs the gnu software to be the system they care about. (There can be controversies on whether gnu is needed or not, since it’s possible to create a distro without the coreutils, but let’s not get you confused right now)
5 years already? Shit, I’m old.