I don't even think it's really possible to avoid it all, GNU libraries/compilers/... are used by pretty much everything that's not on Windows platform. You'd basically have to write all your software yourself.
Well if you ever printed from OSX then you used CUPS which is a GNU tool. The shell is filled with them, if you ever used bash you used a GNU tool. You might say I never used that stuff directly but GNU libraries, shell scripts etc... are built into so many other applications that it's hard to not use any at all. Most applications written in C on the mac are probably compiled with gcc that means they have gnu code in them. I'm not 100% sure but doesn't all iOS app also get compiled with gcc? Xcode includes it as the default compiler.
Apple has done a good job hiding those things from us to build a user friendly operating system and tools on top but at the bottom there a bunch of GNU tools.
I guess it depends how gnugan you want to be. But it's probably got some GNU code in everywhere.
