THe bigger problem with ZFS on Linux imho, is the NIH (Not Invented Here) syndrome that is so chronic in Linux.
It wasn't developed originally as GPL, and thus the Linux guys need to reinvent the wheel. See: DTRACE, ZFS, etc.
For what its worth (from what I've read), the Sun developers of ZFS appear to believe there's nothing in the CDDL itself that would prevent inclusion in Linux.
If the GPLv2 is so stringent on linking (only link to GPL code) then surely this would also preclude the operation of non-GPL binaries on Linux as well?
The Linux guys appear to have no problem linking to binary blobs for Nvidia driver support?