"Not completely. Proprietary modules and forks of both exist, so in the broadest sense they are not (in the sense of, if I'm ever handed a copy of something calling itself LLVM, I do not know that it is libre software)."
Proprietary forks and modules of GCC exist too.
Shocking, I know.
Well, if they do they're never distributed, so a better term would be private, not proprietary.
I suppose in the corporate sense, these two things are indistinguishable, so I should specify that I meant non-free, in the free-as-in-freedom sense, but I don't think I was ambiguous.
I've been having this conversation in good faith, though my opinion is unpopular, and I'd invite you to do the same.
Proprietary forks and modules of GCC exist too. Shocking, I know.