GPLv2-Only Compatibiliy

Question

I like to make my work public by using GPLv2-Only. This because its pretty clear with the copyleft: Use my work for whatever purpose you want, but if you change it or make it better, give it back ;-)

This of course is my personal opinion and other people have other licensing preferences.

So here is my question:

I work a lot with other projects, so i use other peoples libraries and integrate them into my solution.

Mainly MIT and GPLv3+. If i use their work, i assume i need to publish under the same license, so if they used the permissive license MIT, so does also my code need to be published as MIT, same for GPLv3+.

Is this correct?

To be clear, i am not touching the libraries I'm adding to my project, i just add my code to it and create a program of it. If possible i would like to keep my code GPLv2-Only, which respects the ownership and usually makes great open source projects! (Go GNU/Linux ;-))

So is this compatible?

A.) My-GPLv2-Only-Solution + MIT Lib

B.) My-GPLv2-Only-Solution + GPLv3+

Answer 1

A.) My-GPLv2-Only-Solution + MIT Lib

Yes, this is compatible. The combination must be licensed as a whole under the GPLv2, and the MIT parts do not impose any restrictions that make this as-a-whole licensing a problem. You can follow both licenses simultaneously, so they are compatible.

B.) My-GPLv2-Only-Solution + GPLv3+

This combination cannot be legally distributed, because the GPLv2 says the work as a whole must be GPLv2-licensed, while the GPLv3+ says the work as a whole must be at least GPLv3-licensed. You cannot satisfy both requirements simultaneously (notably, the GPLv3 imposes requirements that are additional to GPLv2's, and the GPLv2 does not allow this) so you cannot distribute these components together.

If you are willing to license under the GPLv3 (or GPLv2+), then you can combine your work with GPLv3 libraries. If you remain under GPLv2 only, the world of GPLv3+ libraries is not available to software you wish to distribute.

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You say your chief concern is with copyleft, so I'll note that the GPLv3's copyleft terms are identical to those in GPLv2. Version 3 introduces important updates to its existing mechanisms, e.g., allowing source sharing over a P2P network and allowing compatibility with other licenses' terms that forbid unauthorized trademark use. It is true that the GPLv3 includes some significant new mechanisms like limited patent retaliation and disallowing use of GPLv3 code in hardware devices that refuse to run unauthorized changes (called "tivoization"). However, even significant changes such as these do not affect copyleft source-sharing obligations, which are, again, identical to those in GPLv2.

However, both GPLv2 and GPLv3 only impose copyleft requirements when someone distributes your software. Anyone is free to make private modifications and may offer those changes only to other people who actually receive the software (which may possibly be set of zero people). This means that companies may use GPL software to offer network services without distributing the software or source code. If you want to prevent this case, you may license your code under the AGPLv3, which requires source disclosure to anyone who interacts with a modified version of the software over a computer network. AGPLv3-licensed software can be combined with GPLv3 software by special explicit allowance in both licenses.

Answer 2

Firstly, the GNU Project advises against using the term “MIT licence”, as it is ambiguous. See their comments on the Expat and X11 licences.

Now, on with the question:

I like to make my work public by using GPLv2-Only. This because its pretty clear with the copyleft: Use my work for whatever purpose you want, but if you change it or make it better, give it back ;-)

Normally, I try not to question the OP’s opinion. But in this case, I will. Why not GPLv3-Only? This seems equally clear on the copyleft aspect, but greatly increases compatibility.

If i use their work, i assume i need to publish under the same license

No, you need to publish under a compatible licence.

For example, say you combined an GPLv2-Only work with an MIT work and released the combination as GPLv2-Only. Your users would need to comply with the GPLv2 requirements, and in doing so would automatically comply with the MIT requirements too. This is all legal; these licences are compatible.

But GPLv3 requires modified versions to be under (A)GPLv3 as well. And GPLv2 requires modified versions to be under GPLv2. So you cannot comply with both licences at the same time; these licences are incompatible.

If possible i would like to keep my code GPLv2-Only

If you use an MIT library, this is possible.

If you use a GPLv3 library, you need to release the combination under (A)GPLv3. From this, users can extract your code, which will still be under (A)GPLv3. So it is not possible to keep your code GPLv2-Only. It can still be GPLv2, just without the “only”.