I think ubuntu has a good argument[1] that it can still be shipped as a separate kernel module and satisfy both licenses.
"The CDDL applies to all files under the CDDL, while the GPLv2 applies to derivative works. The CDDL cannot apply to the Linux kernel because zfs.ko is a self-contained file system module — the kernel itself is quite obviously not a derivative work of this new file system."
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I think ubuntu has a good argument[1] that it can still be shipped as a separate kernel module and satisfy both licenses.
"The CDDL applies to all files under the CDDL, while the GPLv2 applies to derivative works. The CDDL cannot apply to the Linux kernel because zfs.ko is a self-contained file system module — the kernel itself is quite obviously not a derivative work of this new file system."
[1] https://ubuntu.com/blog/zfs-licensing-and-linux