I don't think it has much to do with the license, CDDL is based on Mozilla Public License after all (https://en.wikipedia.org/wiki/Common_Development_and_Distri

I don't think it has much to do with the license, CDDL is based on Mozilla Public License after all (https://en.wikipedia.org/wiki/Common_Development_and_Distribution_License https://en.wikipedia.org/wiki/Common_Development_and_Distrib...). The license being different to the kernel prevents distribution of kernel images with inbuilt ZFS support, but this can be worked around by installing it later, just as they already do with proprietary GPU drivers.