grub2 boot root-on-zfs errors

[Beeblebrox]

>> I dare to guess - install zfs library.

My system is FreeBSD - separate zfs library is a linuxism, since in
FreeBSD zfs is part of base source (/usr/src) and vannot be installed
as a separate package unlike in linux.

If you mean here that grub has separate zfslib source code, I have not found it.

>> it is used only to build user level utilites
What are those utilities, like zfsinfo in grub command-line?