[merijnv]

Dude, that's literally what "licenses are incompatible" means.

The GPL gives you a license to distribute IF AND ONLY IF all the linked binaries have AT LEAST the same permissive rights as the GPL mandates. The CDDL gives rights SIMILAR to GPL, but in a way that is incompatible, i.e. which does not let you distribute CDDL code with all the permissions the GPL mandates. As such, you void the license to distribute the GPL code, as you're unable to comply with the GPL license (i.e. the bit that all linked binaries have at least the GPL enforced liberties).

The GPL's license to distribute is dependent on you distributing binaries with the appropriate permissions and the CDDL won't let you.

[insaneirish]

If it was a legal issue, everyone would be scared of shipping not open graphics drivers as well.

Richard Yao from Gentoo summarizes it quite well (http://phoronix.com/forums/showthread.php?79312-ZFS-On-Linux...).

I don't think lack of manpower has been the only thing preventing it. I think idealogical issues are the main factor.

[merijnv]

Shipping non-open graphics drivers together with the linux kernel is a violation of the GPL. Providing non-open binaries separately from the linux kernel is not. The GPL only applies to distribution, if you're not distributing GPL code (for instance, only your non-open drivers) there's no problem.

The GPL puts no restrictions on use, i.e. once you've got both linux and your non-open drivers the GPL doesn't care whether you combine the two.

Additionally, as people point out the license can only be enforced by copyright holders, so if no linux copyright owners bother to sue people distributing non-open drivers, nothing will happen.

This is however rather shaky legal ground, as at any point you could get sued for violating the license. This also why linux doesn't ship ZFS, since the CDDL is incompatible with GPL any company distributing linux with ZFS would open itself to a potential lawsuit by any linux copyright holder. You can imagine most companies are not very happy taking this risk.

With regards to Richard Yao's comments, of course he's not worried. Copyright violation (which is what breaking the GPL is) only lets you sue for monetary damages or to stop the distribution. There's zero reason for people to sue most linux distros as they're non-profits that aren't charging for distribution. Since it's nearly impossible to show monetary loss by a linux copyright holder (it's being distributed for free!) The only thing to possibly do would be to sue the distros into ceasing distribution, which seems an undesirable outcome for most linux copyright holders, so that's unlikely to be enforced.

Since GPL doesn't restrict actual usage the users of these distros have nothing to worry about anyway.

In summary, you only have to worry about being sued if you are both violating the GPL and making some sort of money while doing it. But the fact that you probably won't get sued doesn't mean that what you are doing is not illegal.

- Well, in any country that's signed the Berne Convention, anyway.

[lucian1900]

There is no issue with non-free drivers, since they are explicitly licensed by the copyright owner to be redistributable by anyone and they explicitly installed/enabled by users, so Linux's license is also satisfied.

ZFS could be shipped in a similar manner to drivers, by requiring explicit user action to enable (I believe this is what Gentoo are doing). However, it makes a lot less sense for a filesystem, since the switching costs are much higher than for a graphics driver.

[insaneirish]

It makes exactly the same sense! The installer could require explicit user action to pick ZFS. And there you go, the root filesystem would be on ZFS.

[lucian1900]

While Linux copyright owners generally allow the (small) breach of GPL that is shipping GPL-incompatible modules (whereas it would be entirely fine if they were installed separately) and the driver copyright owners also explicitly allow redistribution, ZFS's copyright owners have made no such allowance.

It would at least breach ZFS's license to ship it.

[belorn]

A license is only as enforced as the author want it to be.

In the case of Linux, the author has expressed an explicit opinion that most linux+driver combination do not create a derivative work.