Can a license protect against future threats to computer user freedom?

Software is free when you are free to run, copy, distribute, study, change, and improve it. The Free Software Foundation (FSF) recommends copyright holders use the FSF's GNU family of licenses to free their programs. We are the stewards of these standard free software licenses, which we designed with care and in cooperation with the community and lawyers to ensure they perpetuate software freedom. GNU licenses explicitly grant the freedoms as defined in the Free Software Definition. Our licenses include copyleft clauses which ensure that users can exercise these freedoms in derivative works, such as improvements and combinations (by requiring that such works are subject to the same license).

Generally, it is not easy to change a program's license. Relicensing requires consent of all copyright holders, who can be numerous given the collaborative development of free software. This is good news for users, who can rest assured that their freedoms cannot be easily revoked. But it may become a problem if the license becomes outdated, for example, when new threats to user freedoms are identified which a new license can address more specifically. A new version of the license can be drafted, but it will not automatically apply to programs released under the old one, unless it is explicitly made possible by the copyright holders.

In fact, explicit permission for users to switch to a newer version of the license is the FSF's recommended way of applying any of the GNU family of licenses. The recommended notice template for the GNU General Public License (GPL) v2 and v3 (placed in the "How to Apply" section just below license terms) includes the following wording:

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version [2 or 3, respectively] of the License, or (at your option) any later version.

The license notice is a statement by which copyright holders communicate the terms of their choice in each particular source code file. If someone chooses to draft a different notice, with no explicit "or any later version" language, users have to follow the version number of the GNU GPL specified in the notice.

Section 14 of the GNU GPLv3 (and Section 9 of the GNU GPLv2, which uses almost the same language) provides some important guidelines for interpreting license notices. Its pertinent part reads:

The Free Software Foundation may publish revised and/or new versions of the GNU General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

Each version is given a distinguishing version number. If the Program specifies that a certain numbered version of the GNU General Public License “or any later version” applies to it, you have the option of following the terms and conditions either of that numbered version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of the GNU General Public License, you may choose any version ever published by the Free Software Foundation.

There are at least two important rules that follow from this:

• The preferred way of allowing users to choose a newer version of the GNU GPL is by using "or any later version" language in the license notice; and
• License notices that do not specify a version number should be interpreted to allow the user to choose any version of the GNU GPL;

Allowing the users to choose any later version of the GNU GPL protects them better against future threats. Another important benefit of the choice is license compatibility. Two licenses are compatible when they permit programs released under these licenses to be combined into a larger work. Different copyleft licenses are rarely compatible with each other, and it is especially the case with strong copyleft licenses. In particular, the GNU GPLv2 is not compatible with the GNU GPLv3. The problem can be solved by releasing a program under "the GNU GPLv2 or any later version", which allows users to choose the GNU GPLv3 whenever they want to combine the program with another program under the latter license.

The FSF has strong safeguards implemented to ensure that new versions of the GNU GPL will remain free software licenses. The FSF's by-laws require a supermajority vote of 66% of the Directors at a Special Meeting of the Board to direct the President of FSF to start a drafting process for any new copyright license or a new version of an existing license, as well as to publish them when they are finally ready. Members of the Board are bound by the Code of Ethics, and also, the GPL drafting process is public and transparent.

Additionally, the following license terms address future concerns of freedom, for your consideration:

• Sec. 14 (GPLv3) and Sec. 9 (GPLv2) announce new versions that would be "similar in spirit to the present version." If, a newer version does not keep the free software spirit, lawyers could argue that the permission to follow a newer version does not cover such a version.

• The "or any later version" introduces an alternative upgrade, not a forced one. Users can still opt for the older version of the GNU GPL, which still grants them their freedom.

To sum up, can a license protect your work against future threats to computer user freedom? Yes. Any version of the GNU GPL provides a strong level of protection. But it may be insufficient against unforeseen future threats. We believe that if you use one of the FSF's GNU licenses together with the FSF's recommended license notice that includes "or any later version" language, you will get the maximum legal protection possible for freedom.