Hacker News Reader

Comment by davexunit | Hacker News Reader

Sorry to be a downer folks, but Canonical is violating GPLv2 by merging ZFS into their kernel tree. The CDDL and GPL are incompatible.

https://twitter.com/mjg59/status/700073945064611841

View on HN

Comment by Richard Yao, Gentoo dev and ZFS On Linux contributor [1]:

    ... there is no legal issue preventing the sources
    from being combined because neither the CDDL nor
    the GPL place restrictions on aggregations of
    source code, which is what putting ZFS into the
    same tree as Linux would be. Binary modules built
    from such a tree could be distributed with the
    kernel's GPL modules under what the GPL considers
    to be an aggregate. These concepts have passed
    legal review by many parties.

[1] http://www.phoronix.com/forums/forum/software/general-linux-...

"However, there is nothing in either license that prevents distributing it in the form of a binary module or in the form of source code."

http://zfsonlinux.org/faq.html#WhatAboutTheLicensingIssue

Whether any loadable kernel module can be licensed under a different license than the GPL is still up for debate (even Linus says "sometimes"):

http://www.tldp.org/HOWTO/Module-HOWTO/copyright.html

(Of course, Ubuntu et al have been doing this for years e.g. with Nvidia or HBA binary blob drivers, so it does appear to be a mostly-settled issue..)

This was settled with the Andrew filesystem, which is a matter that I do not believe Linus considers up for debate. ZFS being a port from another system just like the Andrew filesystem is naturally in the same boat.

I'm going to go out on a limb and say that Canonical were aware of this and have found a solution.

That said, I'd be interested to see what the solution was.

They don't need to merge it into the kernel though. If it's installed as a kernel module post installation, it doesn't violate GPL.

>They don't need to merge it into the kernel though.

Then could you explain what this commit is:

http://kernel.ubuntu.com/git/ubuntu/ubuntu-xenial.git/commit...

Canonical cannot ship ZFS in binary form. Kernel modules are derivative works of the kernel, and thus they must be distributed under GPLv2.

ZFS is not a derivative work of the Linux kernel seeing as it was developed on Solaris and later Illumos.

ZFS on Linux doesn't work unless it's linked against interfaces provided by Linux. This is a derivative work, and thus the combined work must be distributed under GPLv2.

GPL doesn't stop you from linking post installation. See http://zfsonlinux.org/faq.html#WhatAboutTheLicensingIssue

Userland software doesn't work unless it can use system calls provided by the Linux kernel either.

The kernel copyright file expressly states that using the standard system call interface does not create a derivative work. There is no such statement about in-kernel symbols.

That's a good assurance that would probably estop a Linux copyright holder from later claiming that a binary using only the system call interface is an infringing derivative work.

It doesn't have the power to define a binary module using an internal interface as a derivative work; that can only be done by a court interpreting copyright law in a particular jurisdiction. In the United States, different Federal Circuit courts have different views of what constitutes a derivative work in software.

> The kernel copyright file expressly states that using the standard system call interface does not create a derivative work. There is no such statement about in-kernel symbols.

There is no legal precedent suggesting that was actually necessary either. Or are you aware of a court case

Linking does not matter for the GPL. What matters it he legal concept of a derivative work. It just so happens that linking to a dynamic library bears a strong resemblance to a derivative work. LKMs and plugins in general are an entirely different matter. GPL software that supports plugins implicitly allows proprietary software to be loaded into it. That is why the FSF had been opposed to allowing plugins in GCC for years until competition from Clang required that they become more tolerant or face irrelevance.

That being said, would anyone who believes this "linking to the kernel" argument please explain what linking actually means and how it is related to the GPL when the term "link" is not even present in the GPL?

Kernel modules are not derivative works of the kernel under copyright law (which was originally designed around literary works). Some might argue that kernel modules that were developed on Linux are, but ZFS itself is ported from another platform, so that is a moot point.

The only case where you cannot distribute ZFS is if you link it into the vmlinux binary that your bootloader loads. In that case, it is no longer a LKM and you can claim the binary is a derived work of Linux. That is what I believe shmeri meant.

> Canonical cannot ship ZFS in binary form.

Building kernel module on the fly when deploying ZFS is an acceptable workaround. I think that's exactly how it was planned to be used in Debian. I really have no clue what Canonical are planning though.

A user editing the wiki posted incorrect information that he inferred from the use of DKMS. It happens.

NO VIOLATION! Sorry but Cannanicol has annoucned OpenZFS http://open-zfs.org/wiki/Main_Page The wiki page is ZFS edited in Dec and not OpenZFS

Is it distributed under the GPLv2?

No, and it effectively never will be.

See: http://open-zfs.org/wiki/FAQ#Do_you_plan_to_release_OpenZFS_...

Reply on news.ycombinator.com