There's nothing apple-esque about any of this. 'If you're unhappy fork it', is a common adage that is definitely applicable here.
You cannot fork systemd in practice; it's enormous, and its components are tightly coupled with complex, non-stable interfaces between them. So while you have access to the source code, you do not have the practical ability to exercise the FSF's four freedoms.
GNU/Linux was created as a rewrite of Unix not because Unix was the best operating system around, but because it was a design that could be replaced, changed, and improved piecemeal. GNU were able to write improved open-source versions of the components of a Unix system - such as init - piece by piece, and test them out and use them on existing Unix systems, rather than having to rewrite everything before they could do anything. If those older Unix systems had been designed like Systemd, that would not have been possible, and Linux would never have got off the ground.
GNU is a bunch of utilities no different than various terminal programs. The attempt at the "GNU OS" failed because the Hurd was never really usable.
Pre-systemd you could get Debian with Hurd and it was fine. There was never much reason to use it - hardware support was worse than Linux and there was no real killer feature in practice - but it worked.
No it didn't: GNU / Linux is a huge success.
I think the main reason that there isn't a systemd fork is that it's just not particularly worth it: it works well enough for enough people that no-one is motivated enough to try to improve on it outside what the project is doing anyway. And those that do strongly object to it tend to reject the whole approach and so they start from scratch, and then lack traction because they don't interoperate at all.
It's not modular and when other packages assume it's there it starts to become difficult to remove it. So where's the choice in that? This is just Linux becoming a corporate thing - going in whatever direction the big players want. When money is involved it seems to generate some quite dismissive attitudes.
On the good side, there are non commercial distros already with more than acceptable alternatives and I am using one of them now (with dinit - very nice). I'm not suffering. I have a distro that is far less complicated than Fedora and vastly easier to fit to my needs...and actually faster too. I hope we can avoid Linux becoming Windows or the Mac. Desktop domination is a silly goal - if it happened it would only result in a similarly locked down and unsatisfactory system without choice.
Morally there's no equivalence here.