I think Fedora will continue to be fine for the foreseeable future as it's an upstream OS. It gets changes before they go into an RHEL release, which means a Fedora user is essentially beta-testing future RHEL changes. There's nothing inherently wrong with that and if you're happy on Fedora then you can stick with it and be confident it's going to continue to operate the way it does today (barring any future licensing changes from IBM that affect upstream distros).

This change will really affect the downstream distros like Rocky Linux and AlmaLinux. I think those distros have a valuable place in the FOSS ecosystem, as they allow FOSS contributors a low-friction way to test their code on an RHEL-compatible distro without having to agree to a Red Hat license. The fact they IBM / Red Hat is making this change must mean that they see some advantage in having absolute control of the licensing terms for downstream distros, and I have to imagine that their gain will be at least partly at the community's expense.

Is this the beginning of yet another corporate enshitifcation?

I hadn't actually thought of this as enshitification, but upon reflection... yeah, it truly is! Red Hat allowed the existence of downstream distros, and even made one of their own in CentOS, because they understood how supporting FOSS dev/test on their enterprise product ultimately increased the overall value of that product to their paying customers. Now that IBM has bought Red Hat they don't care about any of that, they just want to squeeze as hard as possible to maximize the return on their investment. I'd say enshitification started in earnest when they killed CentOS six months ago, so the current announcement is the second phase of enshitification.

But it's not "getting closed", that's a misleading headline that people have jumped on all of a sudden, there was no talk of this yesterday when the change was announced. This was the original wording. Nothing is going closed, the way it's published is changing - you might not like the change, but to call it closed source is just deceptive.

The worst case (most cynical interpretation of Red Hat's narrative) is that they're trying to make things difficult for Rocky and Alma (which doesn't make much sense to me from their point of view but it's what it looks like). The best case (most charitable interpretation) is that it's a simple rationalisation that could encourage better community integration.

Of course if people keep spreading false or sensationalist narrative that might harm their reputation anyway through misinformation (which is kind of what happened with CentOS Stream in my view).