Re: @WolfFan - just downloaded
Re: "the GPL also dictates how the software must be distributed"
Well yes and no! From what I can see the GPL doesn't limit me to what I can put on a CD/DVD for distribution. Hence, it seems I can sell a disk with a Linux tarball and a whole bunch of other stuff (ie. tarballs) with incompatible licences burnt onto it without falling foul. Also the GPL doesn't seem to prevent me using either a proprietary installer or an open source one with predefined/default preferences to front the installation of my CD/DVD's contents - and what is a CD/DVD by just a convenient hardcopy snapshot/cached copy of a network install...
So it would seem that the real question is exactly how Canonical have included ZFS in its Linux distribution.