This shift means that there will be little to no net new development of Illumos. While working through the git history of ZoL I have also discovered that many races and locking bugs have been fixed in ZoL and never made it back to Illumos and thus FreeBSD. This state of affairs has led to a general agreement among the stakeholders that I have spoken to that it makes sense to rebase FreeBSD’s ZFS on ZoL.

Also some background: https://lists.freebsd.org/pipermail/freebsd-current/2018-December/072430.html

source: L