[merijnv]

Of course not, that'd be a violation of the GPL. They ship their own fork/patched version of bash, whose source is on their open source page: https://opensource.apple.com/source/bash/bash-118.11.1/

[solarkraft]

So ... rootless.h does nothing? I can compile a bash without it that does exactly the same thing? That seems like it would contradict previous comments. What am I not getting?

[bonzini]

It contains the declaration of a single function from macOS's libc. You cannot compile Apple's provided bash sources at all without it, but it's trivial to work around the missing header.