A recent discussion on the lkml examined the possibility of a Linux implementation of Sun's ZFS. It was pointed out that the file system is released under the GPL-incompatible CDDL, and that Sun has filed numerous patents to prevent ZFS from being reverse engineered. Max Yudin pointed out, "according to Jeff Bonwick's blog Sun issued 56 patents on ZFS, but I have no idea what they patented. Sorry, binary compatible ZFS reimplementation with GPL license might not be legal." David Litwin noted that he had been told by a ZFS developer to talk to Linux developers to see about getting non-GPL'd code included with the kernel. Theodore T'so replied, "that was totally useless answer from the ZFS developers. What he should have told you is to contact Sun management, since they are the only ones who can decide whether or not to release ZFS under a GPL license, and more importantly, to give a patent license for any patents they may have filed in the course of developing ZFS."
Alan Cox [interview] suggested, "the real test of whether Sun were serious about ZFS being anywhere but Solaris is what they do to license it - they've patented everything they can, and made the code available only under licenses incompatible with other OS products. Their intent is quite clear, and quite sad. Compare it to what the old Sun company did with NFS, which is now a standard used everywhere." Theodore T'so added, "given that Sun has reportedly filed a huge number of patents covering ZFS and has refused to make them available for anything other than Solaris --- and there are senior Sun programmers who have on record stated that one of the reasons why Sun picked the CDDL was precisely because it was incompatible with GPL and Sun fears Linux ---- I wouldn't bet on Sun being willing to making a patent license available to a hypothetical alternate implementation of the ZFS format for Linux." He went on to note, "of course, this is all open source. If someone wants to work on reimplementing ZFS from scratch, either in userspace or in the kernel, certainly the Linux community won't stop them. Given the patent issues Linus might not feel comfortable including it in the mainline sources without a promise from Sun that they won't sue the pants off of him and The Linux Foundation, but again, that's Sun's decision, and no one else can help you there."