If a project is licensed under GPL-2.0-or-later/MPL1.*, to what extent could the FSF/Mozilla releases a new version that imposes obligations or removes protections for licensors?

Some examples:

  • Could a future version replace the normal warranty disclaimer with something like "The authors accept full liability for any damages caused by the software" (or even just removing it)?
  • Could a future license impose requirements on the licensor? As an extreme example, consider terms like, "By using this software, the licensor agrees to pay you, the licensee, $100".
    • Consider especially jurisdictions that have affirmed the GPL's status as a contract in addition to a license.
  • Could future versions contain targeted forms of the above terms, like, "Only if this software is being licensed by 9t8, then licensor agrees to pay licensee $100"? Or any other criteria, like "if this software was downloaded from GitHub.com", etc.

Some specific questions:

  • Do the licenses themselves contain any limits on what future versions might allow or require?
  • Does contract law have an obvious consideration that might limit the introduction of such terms (e.g., the option to nullify a radically different contract terms offered automatically by "or any later version" language)?

Of course, some of these examples are more far-fetched than others, but I'm interested in the legal bounds of what is actually possible (rather than socially likely).

  • 1
    Related (though without testing the full limits of what would be legally possible): Is it possible that a future GPL version removes copyleft? (the FSF did target Wikis in their update to GFDL, though it was more or less at their insistence)
    – apsillers
    Jul 20, 2022 at 11:21
  • How would the FSF/Mozilla be mounting a "targeted attack" by changing a license? The license would affect all projects using the license equally, thus by definition, could not reasonably be targeted. I suppose, hypothetically, they could change the license to say everyone is exempt from this change except "9t8", but I think the odds of being struck by a meteor 10 times within a single week are greater. Jul 21, 2022 at 3:25
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    @98t The (likely unenforceable) conditions of reading this comment are that you give $100 to charity every day. If that type of exceptionally unlikely hypothetical is your concern, I think writing your own license is likely your best solution. If your interest is asking academically about hypothetical possibilities, I think the answer is that technically anything is possible, but you'll need to consult with legal experts as to what is legally enforceable in your jurisdiction(s). Jul 21, 2022 at 8:29
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    @9t8 I've itemized what I think are your question's main legal considerations (and affirmatively disavowed social concerns); please feel free to edit further if I've gotten anything wrong.
    – apsillers
    Jul 21, 2022 at 14:55
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    @98t Sorry if I'm missing something obvious, but how would you be "...explicitly agreeing to it by saying so in the license header of every file in the project."? Are you saying you would intentionally write "I agree to the license" in every file in the project? If so, why write something like that? Jul 22, 2022 at 8:02

4 Answers 4


There is some risk, but perhaps not as much as you think.

Hypothetically, let's say the FSF release v4 of the "GNU GPL" which has identical wording to the MIT License. At this point, it is the case that anyone could take code released under the earlier versions of the GPL and licensed with the "or later versions" and ignore the copyleft aspect. While the FSF aren't likely to make that v4, they may make a v4 with clauses you don't like, much as some people don't like some of the clauses in the GPL v3 so you are taking on that risk.

However, even if the FSF released a v4 which was just v3 of the GNU GPL which an additional clause "9t8 must pay everyone receiving this software $100", that would have no effect as it goes beyond the bounds of what a copyright license can enact and would require an explicit agreement from you, just the same as if I released some software under the "PK License" which had the same clause without you agreeing to it.

On the other hand, "or later versions" gives you some protection as well. For example, if you think tivoization is bad, allowing people to upgrade code from GPL v2 to GPL v3 is a good thing. Basically, it comes down to whether you think it is more likely that there will be a "bug" in the license, or the organisation owning the license.

  • 1
    What is the line between clauses that require implicit or explicit agreement? Which side of the line would the examples in the question fall on?
    – 9t8
    Jul 20, 2022 at 7:59
  • 2
    @9t8 As a question regarding the overlap between copyright and contract law, that will be jurisdiction and case dependent. Jul 20, 2022 at 8:03
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    Can you edit your answer to reflect this (and to maybe remove the off-topic last paragraph)?
    – 9t8
    Jul 20, 2022 at 8:33
  • 8
    IMO the last paragraph is highly relevant and should be left.
    – Reid
    Jul 20, 2022 at 15:35
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    Insofar as your question is "what is the maximal legal reach of an or-later-versions clause?" I agree it's off-topic, but insofar as your question is "Is it safe to use a license that allows later versions?" a consideration of safety (i.e., risk) of whether to make a binary choice ought to consider the risk that may arise from not making that choice.
    – apsillers
    Jul 20, 2022 at 22:14

You seem to be referring to the following part of the standard GPL license notice:

Copyright (C) <year> <name of author>

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 of the License, or (at your option) any later version.

Note that this text is merely the license notice. You're informing the user which license applies to the covered work. This is not part of the license itself. The actual text of the GPL license does not include this ability to automatically upgrade to a newer version. The only thing in the actual license that's similar is the following from section 9:

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

Key here is that the second sentence starts with "if". The "any later version" part of the standard license notice is not a requirement. If you want to make your work available under GPL v2 and nothing else, you should be able to use a license notice that's worded something like:

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; version 2.

If you're uncomfortable with the risks associated with an unpredictable future license, you can always switch. Linux originally was "GPL v2 or later", but key core developers were wary about this exact risk and changed it to "GPL v2 only" before v3 was released.

Note that GPL v3 is a bit better about all of this. Section 7 describes "additional permissions" that can be added to a license, a concept that seems to cover the "or later version" clause in the license notice. Section 7 gives you the explicit option to remove any additional permissions when you redistribute the software (effectively making it easy to drop the "or later version" bit). Also, section 14 includes a paragraph that may have been intended to assuage this particular fear:

Later license versions may give you additional or different permissions. However, no additional obligations are imposed on any author or copyright holder as a result of your choosing to follow a later version.

So for the GPL at least, it looks like the amount of damage a future version could do to you personally is limited. Future versions might give new permissions to users, but can't force you (the author) to do anything you haven't already agreed to do.

The MPL is different. Section 10.2 of the license says that the software can be redistributed "under the terms of any subsequent version". That part isn't an optional term like it is with the GPL, so there's more risk in this case. The MPL does include this in section 2.4, though:

No Contributor makes additional grants as a result of Your choice to distribute the Covered Software under a subsequent version of this License (see Section 10.2)

That will limit the surprises that can happen with a future license version, but (IMO) doesn't seem to be as strong as section 10 of the GPL v3. Older versions of the MPL did not include this clause, and the risk there would be significantly higher. Any booby traps in future licenses would only apply to people who were still using the old versions and haven't upgraded to versions that contain these protections. That's a pool of people that gets smaller every day, and a small target pool makes such shenanigans less likely to be attempted.

More importantly, the only organizations that can release new versions of these licenses (FSF/Mozilla) have published vast amounts of software under every version of said license. Doing something like removing the warranty disclaimer would hurt themselves more than whoever they were trying to attack and makes this sort of treachery vanishingly unlikely.

  • I overlooked that section of the GPL and have edited my question accordingly. Thanks for pointing it out.
    – 9t8
    Jul 20, 2022 at 22:05
  • @9t8 After your edit the answer is still essentially the same: current license versions explicitly protect you. It might be possible with older versions, but the FSF and Mozilla have extreme incentives to prevent that sort of thing from happening.
    – bta
    Jul 20, 2022 at 22:33
  • Which parts of the licenses? Also, what is preventing this from happening, which seems somewhat similar to this?
    – 9t8
    Jul 20, 2022 at 22:39
  • @9t8 - A clause like that would require the person suing you to prove a negative (that you hadn't released it prior). The "28 March 2007" reference in the GPL v3 is the date v3 was released. That clause is included because otherwise that section of v3 would clash with existing contracts between software publishers and their customers, which in some places isn't legal and in others would just make a lot of people very angry.
    – bta
    Jul 21, 2022 at 1:02
  • GPL v3 section 11 is designed to prevent the problems that led to the SCO/Novell/Microsoft lawsuits. If these provisions were applied retroactively to existing contracts, the Free Software Foundation would have been dragged into that decade-long dumpster fire and sued into oblivion.
    – bta
    Jul 21, 2022 at 1:13

Yes, a future update could impose restrictions on future licensors.

You have to consider here that the typical Open-Source license explicitly covers redistribution. That means that the original licensee becomes a licensor themselves.

Now these "upgrade clauses" allow the future licensor to redistribute the software under a new license. That binds them, but not the original licensor.

This is generally not considered a problem, since these upgrade clauses are often optional. Redistribution under the old license remains possible. And if the new license is unreasonable, that's exactly what will happen.

  • It also allows to use the old licence as long as the vX or later clause is not changed to vX+1 or later.
    – allo
    Jul 21, 2022 at 18:50

Clearly not; not in terms of the Question, anyway.

It might be safe if you could explain exactly what all later versions might allow.

Can you, or what?

  • 5
    As it’s currently written, your answer is unclear. Please edit to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers in the help center.
    – Community Bot
    Jul 21, 2022 at 9:17
  • Sorry, ComBot… what's unclear here is the Question. Whether a license allowing later versions could impose obligations or remove protections for licensors in the future is wholly speculative. My Answer, "Clearly not; not in terms of the Question" remains true and who doubts that is welcome to explain the doubt, in terms of the Question. Jul 28, 2022 at 23:23

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