This is where some BSD folks get frustrated by some GPL folks. Compiling code under BSD with code under GPL into the same binary is not _relicensing_. Each section of code still has the same license, and any binaries must abide by the intersection of the licenses. It is indeed the case that the intersection of GPL and BSD is equivalent to GPL and therefore allowed by the GPL, but the BSD license remains on the portions (of code and of binary) that are BSD licensed.
I read it as intersection of the permissions is a union of restrictions. So, I think the point is that given the union of the restrictions, you get the most restrictive license in this case, the GPL.
IANAL, but “GPLv2 or later” allows you (the recipient of the license) to choose either GPLv2 or GPLv3 (i.e. the one that’s more convenient to you) but does not allow you to prevent others (the recipients of your modified version) from having the same choice.
This goes both ways, “GPLv2 or later” cannot be changed to either GPLv2 or GPLv3 only without permission from everybody that has ever contributed to the codebase.
The FSF requires copyright attribution from cotributors, that’s why they were able to switch their projects to GPLv3-only.
(This is not legal advice, but I do deal with software licenses professionally.)
> IANAL, but “GPLv2 or later” allows you (the recipient of the license) to choose either GPLv2 or GPLv3 (i.e. the one that’s more convenient to you) but does not allow you to prevent others (the recipients of your modified version) from having the same choice.
> This goes both ways, “GPLv2 or later” cannot be changed to either GPLv2 or GPLv3 only without permission from everybody that has ever contributed to the codebase.
This is not the case. A dual license allows you to redistribute under one or the other license, or both. "GPLv2 or later" must necessarily allow distributing under GPLv2 or GPLv3, because otherwise it wouldn't be compatible with GPLv2 or GPLv3. You're also free to combine it with GPLv2-only code (in which case you must distribute under GPLv2-only), or GPLv3-or-later code (in which case you must distribute under GPLv3-or-later).
> The FSF requires copyright attribution from cotributors, that’s why they were able to switch their projects to GPLv3-only.
The FSF requires copyright assignment, but that's not why; any project under GPLv2-or-later may be changed to GPLv3-or-later. And new code would then be contributed under GPLv3-or-later.
Also, the FSF doesn't like to use "GPLv3 only", for the same reason they don't like to use "GPLv2 only". FSF projects under GPLv2-or-later switched to GPLv3-or-later.
No, it does not say such thing. “GPLv2 or later” says you are allowed to use it under GPLv2 or GPLv3 (for now). It does not allow to change it to GPL-2.0-only (to use the correct SPDX identifier).
> “GPLv2 or later” says you are allowed to use it under GPLv2 or GPLv3
I am afraid, that you are wrong. GPL does not govern usage of software at all. You don't need to agree to GPL in order to use GPL licensed software. This is literally said in text of GPL itself.
The preamble ("this program is free software...") is not part of GPL itself — it is just short informative text. And you are misremembering, what preamble says. Citing from GNU website:
> 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 3 of the License, or (at your option) any later version.
I believe, that we should erase all SPDX-whatever nonsense from Linux source code, and replace it back with proper preamble — least other users of GPL software start to misremember as well.
> You don't need to agree to GPL in order to use GPL licensed software.
I've wondered for some time how a user is granted permission to use GPL-licensed software; permission is not explicitly granted by the GPL, but it is required so that the user can copy the software to their computer, and into memory for it to be executed, is it not?
(I am aware that the answer will vary by jurisdiction)
The GPL does not explicitly grant permission to use the software, that is true. However, its terms are clear about the conditions in which you lose that right.
the SPDX short identifiers are a great way for people to misunderstand how the license works. The preamble that the FSF suggests makes it clear what it does, why it works that way, and how you can leverage it.
If I take a GPLv2-or-later work, change the license notice to say GPLv2-only (or GPLv3-only, or GPLv3-or-later), and distribute it with that modified notice, have I violated the copyright licenses or copyright law? IANAL but I believe the answer is "No".
Now, if all I've done is change the license notice, my change is legally ineffective – anyone who receives it from me can change it back to the original GPLv2-or-later, and I have no legal recourse against them. However, if at the same time as changing the license, I also make (non-trivial) modifications to the code, then recipients cannot legally change the license back to the original GPLv2-or-later without either reverting my code changes or seeking my permission. (This is because I own copyright in my code changes as a derived work.)
Think about it this way: the license is "GPLv2 or later", not "GPLv2" or "GPLv3". If you change the license notice, you are changing the terms in which people will receive the code from you. The GPL (both of them) clearly says you cannot do this. You have to distribute modified works under the exact same terms you received the original work, or you lose the right to use the software (both original and modified) yourself if you violate its licensing terms.
IANAL. I'm more familiar with GPLv3-or-later because it's how I license Red Moon, but I assume v2-or-later uses the same phrasing, which I got from the FSF website iirc:
> Red Moon is licensed under the GNU General Public License version 3 or (at your option) any later version by the contributors.
As this reads to me, I am offering you a choice of licenses. You may use Red Moon under the GPLv3, or you may choose a later version of the GPL. Or, you could choose both, if you wish to distribute your derivative as GPLv3-or-later.
Put differently, a GPLv2-or-later currently means a dual-license, under both v2 and v3 (and an automatic relicensing to triple license if v4 is released, etc).
The standard wording for a GPLv2-or-later license (as recommended by the appendix of GPLv2 itself) is:
> 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.
Per that notice, I have an option of distributing it under the terms of GPLv2, or under the terms of the GPLv3, or even a GPLv4 if the FSF were to someday publish one. So, I decide to make use of that option and distribute it under the terms of the GPLv3.
You can't argue that from the text of the GPLv2 or GPLv3 that I don't have the option which the license statement says that I do. The license statement applying the GPLv2 (or GPLv3) text is of greater authority than the text of the GPL itself. You can't use the later to cancel out the option granted by the former.
The license is allowing you to perform specific actions. You can modify the work or redistribute it under the terms of "GPLv2 or later" without losing any of the rights the original copyright holder(s) passed on to you.
For a "modify and/or redistribute" example, under this "GPLv2 or later" licensing you can modify the software and use it in a SaaS without having to distribute it (which the GPLv3 would force you to), because you can choose to follow the terms of the GPLv2.
Likewise, you can use it and demand/assume implicit patent grants from the copyright holder, which the GPLv2 says nothing about, but the GPLv3 does.
Changing the license of the work is not modifying the work. That is the key difference. You must pass the same set of rights which you have received, like I said in other places. You can modify the work, but you cannot relicense the work. Only an original copyright holder can do this (for its part of the code).
When someone licenses software under the GPL (any of the versions), he/she isn't giving recipients any rights over licensing, he/she is only defining how the software can be modified and distributed.
Edit: To be clearer, a specific GPL version says you must pass that specific version's rights when you distribute. This makes it look like when you choose a version, you only need to pass that version's terms along. However, general copyright law (in most places) says you need to be explicit, so, if the GPLvX doesn't say you only need to pass those rights, then you need to pass those rights and any other (perhaps optional) rights.
> For a "modify and/or redistribute" example, under this "GPLv2 or later" licensing you can modify the software and use it in a SaaS without having to distribute it (which the GPLv3 would force you to), because you can choose to follow the terms of the GPLv2.
GPLv3 says absolutely nothing about SaaS. You're thinking of the AGPLv3. The only thing GPLv3 does in that regard is declare itself compatible with the AGPLv3, so you can combine code under those licenses.
> How can a license be incompatible with only the latter then?
Your parent comment said no such thing. It says, that you need GPL v3 to be compatible with Apache 2. "Or later" clause on GPL 2-licensed project offers you a way to re-license the project under GPL v3.
