Comment by TheDong | Hacker News Reader

Comment by TheDong | Hacker News Reader

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This is built on a misunderstanding of what the ZFS licensing issue is.

ZFS is licensed under the CDDL [0], which is a copyleft license that grants you full rights to use the ZFS source code for basically anything, providing that any derivative works incorporating its source code are also are under the CDDL. There is no "licensing fee" that you can pay Oracle related to this.

Linux is licensed under the GPL, which just like the CDDL, is a copyleft license which requires derivative works to be distributed under the GPL.

The conflict here is that both require the entire derived work to be distributed under CDDL/GPL, but obviously only one license can be picked.... even though realistically, GPL and CDDL are quite similar licenses.

The additional fact that is useful to know is that zfs.ko, the zfs kernel module, is distributed under the CDDL by ubuntu, and any other distro distributing it that I know of.

So, with that knowledge, who can sue who and why?

1. The people that can be sued are people distributing compiled zfs binaries (the 'zfs.ko' kernel binary). In practice, this means canonical, and anyone else who distributes disk images using ZFS (such as snapshotted EC2 AMIs)

2. The people who can sue are the holders of the Linux GPL license, and they can do so by claiming zfs.ko violates their copyright by being a derived work of the linux kernel, but being distributed under the CDDL rather than the GPL.

So, first of all, the vast majority of companies using ZFS aren't also distributing binary distributions containing zfs.ko and the linux kernel together, therefore this whole thing is moot. Realistically, most companies using ZFS only have the risk of _canonical_ being sued, and that breaking their filesystem, not them running into legal issues themselves.

And second, it would require a holder of Linux copyright to file suit, and realistically, no court could find significant damages here.

Canonical also has lawyers that claim 2 wouldn't legally follow, that 'zfs.ko' is not in fact a derived work of the linux kernel. There's differing opinions there, but pretty much everyone agrees that the people who could sue if this interpretation is wrong is the holders of Linux copyright, not oracle.

[0]: https://en.wikipedia.org/wiki/Common_Development_and_Distrib...

You have one crucial fact wrong: The CDDL is actually a weak per-file copyleft.

The CDDL is totally ok with the rest of the linux kernel staying GPLv2. The GPL is allergic to any non-GPL (eg. ZFS) code being distributed with the kernel source.

Sure, but I don't think that's crucial here.

Does it change any of the other information? I admit I shouldn't have written "both require the entire derived work to be distributed under CDDL/GPL", and instead should have written "both may require, depending on a court's interpretation, the zfs kernel module to be distributed under CDDL or GPL respectively".

I think the rest of the comment stands though, right?

> "both may require, depending on a court's interpretation, the zfs kernel module to be distributed under CDDL or GPL respectively".

That's wrong, and misses fundamental information about the CDDL.

First, the CDDL gives absolutely no fucks how you licence a resulting binary. It only cares about the specific covered source files, and doesn't care what you bundle them with. So nobody would ever argue that the module should be licenced as CDDL.

On the flip side, you'd have a really hard time arguing that the module should be licensed as GPL.* Sure, there's maybe a GPL wrapper, but lots of modules are non-GPL even when they might feature such a wrapper. ie. nvidia. You also can't argue ZFS is a derived work of the kernel, which is really the crux of the issue. ZFS was first written on solaris, developed for several years on freeBSD, and remains neutral across 3-5 different supported OSs. There's nothing to indicate the GPL should have more claim over ZFS than the wrapper.

The one and only place you'll ever run into trouble is if you start trying to distribute ZFS *source code* in the kernel source tree, as a fully integrated part of the kernel. (EDIT: or compiled together in a single kernel binary, from said combined source) The CDDL doesn't care about the mixing but the GPL does. Literally everyone agrees this is a bad idea and nobody does it.

*Let's ignore for a moment for the moment that you *couldn't* since the GPL requires complete corresponding source code and you can't relicence the CDDL source code files.

I agree that statement is factually incorrect, but I still don't think it changes the overall information in my comment in any meaningful way. The actual risk is low, the risk if of GPL infringement, not of oracle suing you, and there are people who contest it on either side. Those are the key points, and those are true I believe.

> On the flip side, you'd have a really hard time arguing that the module should be licensed as GPL

That is the very thing that some people do argue, for example the sfconservancy people. As I note, canonical's lawyers take your view (and I personally agree), but it's not clearcut. The sfconservancy outline their reasoning clearly for why they think zfs.ko is a derived work of the linux kernel.

https://sfconservancy.org/blog/2016/feb/25/zfs-and-linux/

The SFC can get stuffed. Their argument says nothing in particular about ZFS and is essentially "the kernel is GPL and therefore ALL modules MUST BE GPL.

Their stance isn't just rejected by nvidia and company, but also by the kernel devs most notably torvalds himself. Their argument boils down to "if ONLY it were statically linked everyone would say it's derived" combined with "there's no difference between static and dynamic linking."

They completely ignore the inconvenient fact that being statically linked would imply being pasted into the kernel tree, and the real reason people would say it's derived at that point is because you'd expect the ZFS code to be deeply connected with linux's guts if that were the case. Which it isn't, and it isn't. Over in reality courts look at how code came to be and where it came from, a more reasonable definition of "derived." For one thing it means I can't come up with a GPL module that statically links against a pre-existing bit of other software and then try to claim the software should be GPL. (remember, OpenZFS' fork long predates ZFS' compatibility with linux)

Being a derived work shouldn't imply time travel, i.e. at the very minimum shouldn't violate causality.

Torvalds himself has personally refuted the "(dynamic) linking inescapably means you're derived" point on multiple occasions, and yet here the SFC is, continuing to wave it around because that's how they wish it worked.

Their article is very plainly a "extend the GPL's reach" political move attempting to move the goalposts the kernel community set up wrt proprietary modules, while using the muddy waters around ZFS as cover. Their arguments could equally be applied to the nvidia kernel module and yet would instantly be rejected as extreeme if they attempted to use nvidia's module as their subject.

Note that unlike the GPL, the CDDL is file-based. It doesn't require your entire body of software to be CDDL, it just requires that you make modifications to CDDL-licenced files available under the CDDL.

I see, thanks for educating me on this with such an in-depth reply! I simply saw "licensing issue" and "Oracle" together and assumed the standard Oracle licensing worry applied.

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