Google LLC v. Oracle America, Inc.
The code in question was Java code, which has been licensed under (among possibly other licenses) the GPL. The terms of the GPL has not been an issue in the case, but GPL's "virality" AFAIK is premised somewhat on things like API copyrightability.
https://lore.kernel.org/all/[email protected]/...
Quoting from Theodore Ts'o in 2003:
But that aside, does the Open Source community really want to push for the legal principal that just because you write an independent program which uses a particular API, the license infects across the interface? That's essentially interface copyrights, and if say the FSF were to file an amicus curiae brief support that particular legal principle in an kernel modules case, it's worthwhile to think about how Microsoft and Apple could use that case law to f*ck us over very badly.
Similarly, Apple has a policy against shipping GPLv3 code. When bash upgraded to GPLv3 from GPLv2 ~10 years ago, Apple stopped upgrading it, and then eventually migrated to zsh, which is MIT licensed.
The issue is that GPL is a "viral" license, which hasn't been tested all that much in court, but they're erring on the safe side. They don't want to mix their proprietary code with GPL code.