Free Software Foundation published a statement called “Interpreting, enforcing and changing the GNU GPL, as applied to combining Linux and ZFS,” by our founder and president, Richard M. Stallman.
This statement explains why the current license of ZFS prevents it from being combined with Linux. To reach that conclusion, our statement covers all the necessary background for understanding license incompatibilities and violations in general.
In January of 2005, we added to our license list an explanation that the Common Development and Distribution License, version 1.0 (CDDL), though a free license, is incompatible with all versions of the GNU General Public License (GNU GPL). While the CDDL is not commonly used, it is the license that Sun Microsystems (and now Oracle) chose for distributing the file system ZFS. ZFS was originally written for Solaris, but recent projects aim to make it work as a module with other operating system kernels, including Linux, which is licensed under the terms of the GNU GPL version 2.
Normally, incompatibility questions like this are raised by people trying to write proprietary modules for copyleft free programs. They want to benefit from the work done by free software developers without providing others the same freedom, and they treat users unethically. That is not the case here, because ZFS is free software. The ideal solution would be for Oracle, who has become a large and tremendously influential distributor of GPL-covered code, to show their leadership by giving explicit permission allowing their ZFS work to be used under the GPL.
Submitted by: Arnfried Walbrecht