Earlier quoted context omitted.
If the ZFS FreeBSD code are going to be taken from ZoL, what's the difference of use ZFS on FreeBSD and GNU/Linux?
FreeBSD can bundle it in the installer, and put the root filesystem in a ZFS dataset. Because of GPL incompatibility with the CDDL, Linux cannot do this. A compliant installer must put root on something else, usually ext4 or xfs. A Linux installer iso putting root in a zfs dataset opens a terrible legal door.
If said installer downloaded and compiled the code (nvidia-drivers style), you'd not have an issue. Only once the code is combined does it "violate" the license. You can't distribute something in violation of GPL2, but you can keep it for yourself. As long as the installer doesn't distribute offending binaries, you're fine.