There are kernel modules here, which is what I assume they're using:

http://zfsonlinux.org

The licensing problems only apply to distributing CDDL and GPL code that have been compiled into the same binary, not running a CDDL-licensed module in a GPL kernel - I think. My experience with ZFS (which is awesome, btw) comes from FreeBSD.

ZoL looks pretty good - unfortunately if you want Samba on ZoL, of course with snapshots and ACLs, you will have problems, as ACL mapping is not implemented, if I understood things well. That is a real pitty, ZFS is great, Samba is great, Linux is great and having these three things working smoothly together without having to spend weeks of research on how to get it running would help many admins to finally get away from commercial clown & bloat systems. However, the groundwork is done and if we are lucky in 2014 the Linux + Samba4 + ZFS dreamteam will be available as a stable replacement.