"made for GNU" is whatever you misunderstand as "made for Linux", really. because programs hardly ever interact with the kernel, they interact with the userland core of the operating system (e.g. the interfaces specified by POSIX), and that's historically GNU. that's what programs have been written for, even if they're then ported to other GNU-like Unix-like systems. you can probably find and name exceptions to that normal path here and there, but that's what they are: exceptions to the rule.