But a few weeks before release, Sun was acquired by Oracle.
It was going to take months of further negotiations to nail it down. Apple-sourced ZFS on macOS was canceled.
ZFS had been released by Sun before the Oracle Situation under their MIT-like CDDL.
I suppose when Big Tech is involved, they rattle patents at one another until the dust settles with handshakes and payouts all around. I'm speculating here. But I was told that the CDDL was not considered sufficient for Apple to support its own development efforts.
ZFS is relatively complicated, but it generally works. At the time, Apple was shipping servers with iSCSI SAN and a GUI comparable to Disk Utility.
Really a shame. I was running native ZFS on my Mac Pro that summer. Eventually migrated those pools to Open Solaris and eventually to Linux.