They get around the CDDL problem by not distributing ZFS in the kernel. You have to download and build the kernel module separately. Their modifications to ZFS remain under the CDDL licence.
They mention that KQ Infotech are working on the ZFS posix layer here:
"But we believe the way to get around this issue is to build ZFS as a module with a CDDL license, it can still be loaded in the Linux kernel. Though it would be restricted to use the non- GPL symbols, but as long as that rule is adhered to there is no problem of legal issues." Yes, this is a theory that the proprietary drivers are based on too. Afaik it has never been tested in court though.
any news on this ?
did you get a patch ?
The licensing concerns should not be problem because there is a precedence to this and Oracle is already aware of it. The port from LLNL is under US government grant and has been validated by their lawyers. Obviously at first sight it seems like there is problem with the CDDL/GPL issue but as is clearly demonstrated by the port by LLNL and validated by their lawyers porting it as a kernel module is not a problem.