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Choosing a GPLv3-termination Backport to GPLv2

by Bradley M. Kuhn and Karen M. Sandler on May 11, 2019

About four years ago, Conservancy (in collaboration with the Free Software Foundation) published the Principles of Community-Oriented GPL enforcement. Our goal was to conduct our enforcement ethically and respectfully, treating today's violators as tomorrow's contributors. Accordingly, the Principles advocate a holistic approach to GPL enforcement that truly seeks to gain GPL compliance to advance software freedom. We were so happy about the way the Principles assisted the Netfilter team and we were excited that there was substantial interest in codifying these long standing ad-hoc Principles into a widely adopted and published consensus.

Ideas in FOSS also have a way of taking on a life of their own; we share our ideas in the hopes that others will build on them. We have been pleasantly surprised that the last Principle, “Community-oriented compliance processes should extend the benefit of GPLv3-like termination, even for GPLv2-only works”, received so much interest.

This interest led to two independent initiatives to “backport” the GPLv3 termination provisions — by way of an additional permission — to GPLv2-only-licensed works. Additional permissions to GPLv2 have been used for various purposes since the early 1990s (such as for the Bison exception). Additional permissions grant more leeway — relaxing some requirement of the default license — in an effort to reach some policy goal for the project. In this case, the additional permission softens the strict terms of the GPLv2 termination provisions, which state that any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License. That means permissions under GPLv2 are instantly and permanently lost on even easily-correctable violations and require reinstatement of permissions by copyright holders. In contrast, the GPLv3 version gives downstream violators short time periods to comply and receive automatic reinstatement of permissions, via the following clause:

If you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation. Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

This improved policy can indeed be “backported” to GPLv2 via an additional permission.

Two Choices

Two efforts over the last year and a half have “implemented” these backports. The first released was the solution now used by the Linux community, which states:

Notwithstanding the termination provisions of the GPL-2.0, we agree that it is in the best interests of our development community to adopt the following provisions of GPL-3.0 as additional permissions under our license with respect to any non-defensive assertion of rights under the license, However:

[Quotes GPLv3 termination provisions as above]

We call this sub-document the Kernel Enforcement Statement Additional Permission (“KESAP”), as it is published as part of a larger document named “Kernel Enforcement Statement”. (The rest of that document does not contain legally binding terms.)

The second effort, inspired by this KESAP, was released later by Red Hat, which they call the GPL Cooperation Commitment (GPL-CC), but which we will call here “RHCC” to avoid any confusion with FSF initiatives around the GPL and license drafting. The RHCC is available on github.

Adopting One of the Additional Permissions

Conservancy finds both documents intriguing and worthy of additional study and consideration. Moreover, Conservancy has decided that we will adopt one of these GPLv3-termination-backport provisions for copyrights we hold, and advocate adoption for other copyrights held by contributors for our member projects. While we don't demand this of anyone (and won't make use of such an additional permission mandatory for our GPLv2'd projects), we make a strong recommendation for use of a GPLv3-termination-backporting additional permission.

We have for months carefully considered which of the two options is the best to adopt. This was a difficult decision, since the two are similar and both have some problematic aspects. While we applaud both the Linux community and Red Hat for promulgating these useful additional permissions, on balance we prefer KESAP, and so we are adopting and endorsing KESAP. Below we discuss our reasons for this choice between the two for those who wish more detail. Anyone interested can also listen to episode 0x67 of Free as in Freedom where we discuss these issues in detail.

Length and Complexity

KESAP is about half as long as RHCC. When you remove the direct quote in both documents that come from GPLv3's text itself (which obviously must be included in both), the RHCC adds 1,180 words and KESAP adds only 323.

The RHCC is also more complex. It adds additional defined terms, including redefining “We”, which is already a term used in GPLv2's preamble to refer to the FSF. It adds an irrevocability clause, which is not harmful, but it is unnecessary since unilaterally granted copyright permissions are generally irrevocable anyway. Furthermore, given that the word “irrevocable” doesn't appear in GPLv2, adding a redundant irrevocable clause could easily confuse license readers into thinking that GPLv2 itself is otherwise revocable even while the additional permission is not.

Aggressive Defensive Termination Violates Principles

Our biggest concern with both KESAP and RHCC is that they only apply in “non-defensive” situations. This allows copyright holders to fail to provide 30 days for violators to repair violations when those violators are already aggressors in some other form of litigation.

While we are somewhat sympathetic to those who might seek to use GPL enforcement to retaliate against other bad actions, we believe that even potential bad actors deserve the benefit of the doubt and the meager 30 days to repair a violation before facing aggressive enforcement tactics. Furthermore, defensive actions that bring the GPL into court as part of business dispute otherwise unrelated to free software are also the most likely litigation to generate bad legal precedent regarding the GPL. (Indeed, many of the lawsuits that have already been brought over the GPL are in this category. While so far these have settled out of court, there's no reason to expect that to always happen in the future.) We are disappointed that both sets of drafters feel that copyright holders should hold back this permission in those cases. As the Principles state, we continue to discourage any legal action (defensive or otherwise) against a copyright holder who otherwise succeeds in producing a compliant GPL'd source release within 30 days of violation notice. We ask Red Hat and the Linux community to also make this same cure commitment universally, perhaps in an updated version of these additional permissions.

We do note that RHCC is slightly better on this point, since it does narrow non-defensive via a defined term, but it does not narrow it enough to make a real difference, while also adding additional complexity. Moreover, the text specifically mentions legal proceedings and claims, which draws attention to the very activities that make nervous copyleft software adopters skittish.

Additional Permissions Should Not Codify Assent Mechanisms

RHCC has its own orthogonal assent mechanism, based on the presence of a file in the repository. This assent mechanism, while it seems similar to a traditional inbound=outbound regime, is actually novel and untested. The mechanism attempts to gain assent based on a specific date of inclusion of the RHCC file in a repository. Contributors, however, do not necessarily receive any notice of the addition of that file, and therefore their assent is unclear.

For example, imagine a pull request from two levels downstream that waits for merge for months. The modern DVCS-based software development process allows developers to work indefinitely on a forked copy of the repository and there is no way to know that the contributor had a copy of the repository that pre-dated the addition of the file, and they may not have a copy of the RHCC in their repository. When all is merged, it will appear that their commit postdated the addition of the RHCC, but the contributor may be unaware that the exception is added.

Furthermore, many projects already have licensing assent systems that are likely incompatible with one that is baked into the RHCC. Indeed, Linux itself has decided that they cannot make KESAP part of the DCO assent, since too many Linux developers already believe Signed-Off-By means assent merely to GPLv2-only-compatible licensing. The RHCC, when added to a existing project, cannot be adapted to fit a DCO process without modification of the DCO. Since Signed-Off-By tags rarely assent specifically to a version of the Project's DCO, RHCC is incompatible with a DCO-assent-based inbound=outbound assent system.

By contrast, the KESAP is flexible on assent. The entire KES, which includes the actual additional permission that is the KESAP, asks contributors to affirmatively assent with a patch that adds their own name to the file — explicitly indicating assent. Extracted from the KES, the KESAP text can be combined easily with virtually any assent mechanism in use in FOSS today. RHCC simply cannot.

Adding KESAP to your project

Linux is the gold standard of frictionless legal assent that is well-accepted by both individual hobbyists and contributors and corporate contributions and users alike. Recommending the Linux solution to this particular GPLv3-termination backport is simply the best way to quickly promulgate these additional permissions to GPLv2'd projects. We'll be working over the coming months to encourage, and hopefully assist, Conservancy's LGPLv2'd and GPLv2'd (or-later) member projects to implement KESAP. We will also relicense all Conservancy's own GPLv2 (or-later) copyrights to include the KESAP.

Tags: conservancy, GPL, law, licensing

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