I got direct quotes from Apple employees about how their employment has banned them from doing anything related to GPLv3 code in their free time, specifically GCC.
I don't want to mention them in a public website in case that gets them in trouble.
That doesn't surprise me. The GPL, especially v3 and AGPL, are specific weird cases at a lot of companies -- sometimes because they want the freedom to close of forks, but often because they're convinced the GPL/AGPL could "poison" their work and force them to open previously closed source. (This turned out to be a problem for us at RethinkDB, which was AGPL-licensed.)
Well, depending on the employee, it would make sense. Apple funded a large part of clang/llvm, which many assume was specifically to avoid a GPL compiler. You'd hate to accidentally pollute a BSD(-ish) project with GPL code, if your primary purpose for funding the project is to avoid GPL code. Not that anyone would purposefully do such a thing, but it would be important for Apple to even avoid the appearance of anything like that.
I don't want to mention them in a public website in case that gets them in trouble.