Ignoring how Sun/Oracle's shenanigans with ZFS don't nearly account for "90% of their brand damage"...

> simply updating CDDL to allow integrating ZFS with GPL

That can't be done at this point. Owing to a decision that arose right here from a discussion on HN, the ZFS maintainers adopted a policy in 2016 to opt out of the CDDL's built-in "any subsequent version" clause for new source files:

    ~/scratch/zfs$ grep --exclude-dir=.git -Ire "Common Development and Distribution License" -A 2 | grep -ie "\(Version 1\.0 only\|\<only\>.*\<version\>\)" | wc -l
    821

(The CDDL is a file-based license. At the time of that decision, there were already roughly a hundred CDDL-licensed files in the source tree specified as available under "Version 1.0 only".)