The TIL is Red Hat had publicly accessible source code for RHEL. They've removed that and only thing you see is their upstream contributions to CentOS Stream. So you can't build a RHEL counter part at this point, because their source isn't available.
This affects projects like Rocky Linux, Alma Linux, even Oracle Linux.
Fedora runs basically future code for CentOS Stream which is basically RHEL Next really.
Some folks, like I just read Jeff Geerling, are now deciding their code, he makes Ansible stuff, won't be guaranteed on RHEL because they can't publicly test it.
Red Hat is a corporate entity that justifies locking down open sources to satisfy the bottom line. I'm a disgruntled former employee though.
So Fedora is an "upstream" linux. So what that means is developers push their code directly into Fedora. Every 6 months, approximately, Fedora releases a new release. People on Fedora get that and file bugs and features to the next code.
CentOS Stream pulls from that. So they're more stable. They don't have the bugs that the Fedora folks hit (in theory), because it's been solved upstream. By the time it gets to them, down stream, it's been smoothed out.
Red Hat Enterprise Linux every once in a while will put a stake in the ground and say THIS is the code we're going with from CentOS Stream. Make sure THIS version works, and pull in any bug fixes.
To give you a "real" kind of idea. Let's say you have an application. We'll call it the hiya 0.2 version. Fedora pulls in hiya 0.2. Then you keep upgrading until you get to 1.0 then 2.0 then 3.0. Fedora pulls each of those in.
CentOS Stream slowly pulls those in.
Eventually Red Hat says Hiya is what we need in RHEL! Except you're going too fast. We want Hiya 1.0. BAM! Hiya 1.0 is going into RHEL 10. HOWEVER, since you're faster, you've solved bugs in Hiya in 2.0 and 3.0. So RHEL will say well we don't need that feature or that feature or that feature. But we DO need THAT bug fix in 2.0. So we take that bug fix and we backport it into OUR Hiya 1.1 code base. We do need THAT security fix in 3.0 to our code. So we make Hiya 1.2.
This is a VERY simplified version. And I'm not certain anymore on the interaction between CentOS Stream and RHEL. But that's generally how it works.
CentOS was the Free as in beer version of RHEL built from the public RHEL sources.
If you wanted RHEL stability but didn't want to pay for support you often used CentOS
From this article that I just saw in this thread, it looks like they made their Red Hat Enterprise Linux (RHEL) source code unavailable without a subscription through the Red Hat Customer Portal (which I believe requires payment). Essentially it seems that it has gone proprietary.
I'm not 100% in the know on this situation though, so hopefully someone more informed can provide a better answer.
It's not really proprietary. The code is still open. They've just locked it behind a paywall. There is the developer subscription that anyone can get 1 or a few of, can't remember, so you still have access to it. Legally, based on the GPL, they HAVE to give access to their customers.
They also do contribute back upstreams.
But there are somethings they basically put together behind the scenes that would be very difficult for you to do yourself.
I wouldn’t say it seems like they’ve completely gone proprietary because customers still have access to the source code. You may still be able to have access with a free developer account, but I don’t know for sure. Outside of that all of this is news to me as well.