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You are here: Home FSF News Interpreting, enforcing and changing the GNU GPL, as applied to combining Linux and ZFS

Interpreting, enforcing and changing the GNU GPL, as applied to combining Linux and ZFS

by Joshua Gay Contributions Published on Apr 11, 2016 02:54 PM
BOSTON, Massachusetts, USA -- Monday, April 11, 2016 -- The Free Software Foundation (FSF) today announced the publication of "Interpreting, enforcing and changing the GNU GPL, as applied to combining Linux and ZFS," by its founder and president, Richard M. Stallman.

The FSF's statement explains why the current license of ZFS prevents it from being combined with Linux. To reach that conclusion, the statement covers all the necessary background for understanding license incompatibilities and violations in general.

In January of 2005, the FSF added to its 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," said FSF's licensing and compliance manager, Joshua Gay.

FSF's executive director John Sullivan added, "The FSF does not develop Linux and does not presume to tell the developers of Linux when to do GPL enforcement. What we do is provide general materials that make clear the intent behind the GNU family of licenses, and the legal basis for that intent, to create shared and reliable best practices surrounding their use. As this statement makes clear, we support and encourage GPL enforcement work in this area and others when it is done in agreement with these best practices, and in accord with the Principles of Community-Oriented GPL Enforcement."

About the Free Software Foundation

The Free Software Foundation, founded in 1985, is dedicated to promoting computer users' right to use, study, copy, modify, and redistribute computer programs. The FSF promotes the development and use of free (as in freedom) software -- particularly the GNU operating system and its GNU/Linux variants -- and free documentation for free software. The FSF also helps to spread awareness of the ethical and political issues of freedom in the use of software, and its Web sites, located at and, are an important source of information about GNU/Linux. Donations to support the FSF's work can be made at Its headquarters are in Boston, MA, USA.

More information about the FSF, as well as important information for journalists and publishers, is at

About the GNU Operating System and Linux

Richard Stallman announced in September 1983 the plan to develop a free software Unix-like operating system called GNU. GNU is the only operating system developed specifically for the sake of users' freedom. See

In 1992, the essential components of GNU were complete, except for one, the kernel. When in 1992 the kernel Linux was re-released under the GNU GPL, making it free software, the combination of GNU and Linux formed a complete free operating system, which made it possible for the first time to run a PC without non-free software. This combination is the GNU/Linux system. For more explanation, see

Media Contacts

Joshua Gay
Licensing & Compliance Manager
Free Software Foundation
+1 (617) 542 5942

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