"The way it is shipped" differs by distro and the message by non-ubuntu distros is that the way ubuntu ships zfs seems legally risky to them. Ubuntu disagrees a

"The way it is shipped" differs by distro and the message by non-ubuntu distros is that the way ubuntu ships zfs seems legally risky to them. Ubuntu disagrees and they might be right (isle of man jurisdiction IIRC?), but their legal theory has not been tested and oracle has a reputation.