Here is another post from the parent about this issue specificaly:

- http://blog.dustinkirkland.com/2016/02/zfs-licensing-and-lin...

"We at Canonical have conducted a legal review, including discussion with the industry's leading software freedom legal counsel, of the licenses that apply to the Linux kernel and to ZFS.

And in doing so, we have concluded that we are acting within the rights granted and in compliance with their terms of both of those licenses."