There's no zfs grenade. It's CDDL, feel free to use it wherever you want. Oracle can't come after you for violating the gpl even if somehow using zfs on linux violates the gpl.
Most of their legal shenanigans appear to be restricted to companies that already license some software from them.
We have less good laws and systems protecting our right to use software in ways which Oracle considers breach of license.
It doesn't mean they'll win anything in court but they'll ruin you long before they notice the spend.