Canonical's latest release of its Ubuntu Linux distribution includes support for a filesystem that could inspire a legal challenge.
Ubuntu 16.04 contains OpenZFS, an implementation of Sun Microsystems's ZFS file system, currently the property of Oracle. ZFS provides many advantages that are worth having in a server environment, such as snapshotting, copy-on-write, and robust error correction.
But ZFS hasn't been shipped with commercial Linux distributions precompiled since it's licensed under terms that are generally considered incompatible with Linux's GPL.
Before 16.04's release, Canonical took the stance that the CDDL for ZFS had a different scope than the GPL used for the Linux kernel. "The CDDL cannot apply to the Linux kernel," claimed Canonical, "because zfs.ko is a self-contained file system module -- the kernel itself is quite obviously not a derivative work of this new file system."
It's possible to obtain the source and compile ZFS for your own use, but those who spend money on an enterprise Linux distribution support contract generally don't want to deal with the hassles.
The Software Freedom Conservancy believes Canonical's stance violates the GPL because of subtle incompatibilities between the two licenses. The Free Software Foundation, likewise, believes Canonical's use of ZFS in this manner does not adhere to the GPL.
Eben Moglen at the Software Freedom Law Center took another tack. He believed Canonical was in the right by distributing the source for ZFS along with the binary and not adding proprietary changes. "No developer and no user is deprived of any rights that either copyleft license, GPLv2 or CDDL, is designed to ensure and protect," he wrote.
The SFC has urged the copyright holders of ZFS to allow for use with GPL-licensed projects, but so far there's been no official word on the topic. Oracle, which purchased Sun's intellectual property and is generally regarded as the main controlling interest in ZFS, chose some time ago to put its effort behind the development of another Linux file system, called btrfs, rather than aid in porting ZFS to Linux.
Canonical has an indemnification clause designed to shield users from legal fallout from intellectual property disputes, but it's limited to paying customers. It doesn't cover those who use Ubuntu as-is or who create derivative products from it.