[23david]

  In the case of the kernel, this prevents us from distributing ZFS as part of 
  the kernel binary. However, there is nothing in either license that prevents 
  distributing it in the form of a binary module or in the form of source code.

Source: http://zfsonlinux.org/faq.html#WhatAboutTheLicensingIssue

  ZFS cannot be added to Linux directly because the CDDL is incompatible with the GPL. 
  ZFS can, however, be distributed as a DKMS package separate from the main kernel package.

Source: https://wiki.ubuntu.com/ZFS

So why not just distribute the DKMS package with a distro? Easy enough. Will it ruin the user experience somehow?