Modules don't have to be under licences compatible with the GPL. There is no universe where you could possibly argue ZFS is a derived work of the kernel. None.

Modules don't have to be under licences compatible with the GPL. There is no universe where you could possibly argue ZFS is a derived work of the kernel. None. Oracle can't actually sue people using ZFS modules. The CDDL licence that sun provided already gave all the relevant rights away. They can only sue from the GPL side as a kernel contributor, and that's ONLY if someone is dumb enough to ship ZFS code in the linux source tree. You *seriously* underestimate the number of people using ZoL in production that Oracle would love to sue *if they could.*