Someone on Reddit launched a petition to relicense ZFS from CCDL to UPL.
This would make it compatible with the GPL and makes it possible to upstream it into the Linux kernel.
There have been attempts in the past and this will likely fail too.
Anyway,
the Reddit post: https://www.reddit.com/r/zfs/comments/1t24hkj/relicense_zfs_petition/
The petition: https://www.change.org/p/re-license-zfs-to-upl