As others have stated, dtrace has the exact same license and has been in MacOS for years.
They could relicense their codebase, of course, but the number of changes that have happened since they diverged is not small.
Jobs never liked anybody other than himself holding all the cards. Having Ellison and Oracle holding the keys to ZFS was just never going to fly.
(Of course, Jobs may have just decided he didn't want to depend on someone else for the MacOS filesystem in any case.)
ADDED: And as others noted, there were also some storage patent-related issues with Sun. So just a lot of potential complications.
I used it for a while but unfortunately since they are not many people working on this and they are not working on it full time it can take them a good while from a new version of macOS is released until OpenZFS is usable with that version of macOS. This was certainly the case a while ago and why I stopped using OpenZFS on macOS and went back to only using ZFS on FreeBSD and Linux instead of additionally using it on macOS. So with my Mac computers I only use APFS.
I’d love to be a fly on the wall for some of those conversations.
https://www.cnet.com/news/larry-ellison-talks-about-his-best...