It's particularly confusing because "OpenJDK" used to be an independent group who's purpose was to build a fully open-source Java - and it was Apache licensed. Now, it seems that "OpenJDK" refers to a specification and/or working group which NO LONGER provides a build, instead relying on vendors to do so, and indeed the vendors have wide latitude about how they license it.
This is genuinely complicated, I'm not a lawyer or a software license expert, and I don't understand it. And honestly, based on some of the haughty and arrogant, but factually wrong, comments I've been seeing, I suspect that a lot of people think they understand it, but don't.