ZFS (Z File System) is described as a combination of a volume manager (like LVM) and a filesystem (like ext4, xfs, or btrfs), and it’s licensed under CDDL (Common Development and Distribution License). Don’t worry if you didn’t hear about it. It’s not something that’s commonly used.
On the other hand, Linux is licensed under GPLv2 (GNU General Public License Version 2) and these two licenses are not compatible with each other. You can’t use the code from each one in the same binary, and this is where all the confusion started.
ZFS licensing won’t be a problem
The Ubuntu developers are aware of the issues that have been raised by the community, but they figured out this problem before announcing the official support for ZFS in Ubuntu. Canonical’s Dustin Kirkland explained why there wouldn’t be a conflict.
“Equivalent exceptions have existed for many years, for various other stand alone, self-contained, non-GPL and even proprietary (hi, nvidia.ko) kernel modules. Our conclusion is good for Ubuntu users, good for Linux, and good for all of free and open source software,”said Dustin.
In fact, this very issue is explained and resolved on the official ZFS website. In the Q&A section this apparent conflict is also explained. Developers say that nothing in either license prevents distributing it in the form of a binary module or in the form of source code.
Now the community can rest easy that Canonical and Ubuntu are not getting in hot water for their decision to implement ZFS support.
In any case, the fact that people have been asking about this constantly has been reflected in the answer posted by Dustin Kirkland, who says that they’re not really interested in debating license compatibility and they just want to discuss the technology.