I’m thinking about releasing a plugin under the AGPL license.
Would this force people to make public the source code of other unrelated parts of their WordPress installations? (I’ve tried to read the AGPL license but I’m not sure.)
For example, if they install my AGPL plugin, would they have to make available the source code for any other plugins and themes they’ve installed? (Which are probably licensed under the GPL.)
Would it have any legal effects if I publicly stated that I, the copyright holder, don’t consider other plugins and themes and WordPress being part of a combined work? (If other pugins etcetera were not part of a combined work, other people would not have to publish source code for their other plugins etcetera.)
(PS. Since most people aren’t lawyers, I’d take any advice with a grain of salt 🙂 )
I did cast a close-vote, since this question is a duplicate of the indicated question. (A Theme and a Plugin are functionally interchangeable as extensions of WordPress; therefore, any licensing implications of one would apply equally to the other.) That said, I will offer some thoughts.
Caveats:
Now, on to your questions:
As far as I know, GPL and AGPL are written explicitly to coexist peacefully. One does not “infect” the other, and clear boundaries exist between works conveyed in a combination/compilation.
Let’s just use some common-sense tests:
I believe the answer to both of these questions is a resounding “no”.
Let’s set aside question #1, as it probably requires no further discussion.
Regarding question #2: let’s say a user has both your Plugin and the Akismet Plugin installed in their WordPress installation. In what conceivable way is Akismet a derivative work of your Plugin?
Let’s take it a step farther: in what conceivable way is WordPress itself a derivative work of your Plugin?
No. The only thing that matters is the actual text of the license under which you distribute your work. How you personally define “derivative work” doesn’t matter; all that matters is how copyright law and precedent case law define “derivative work”.
Note that, IMHO, GNU fails in this regard also. With the GPL, they define “derivative work” in at least three different ways – but regardless of how GNU defines “derivative work”, all that really matters is how copyright law defines “derivative work”.
I’d say: Perhaps no, not necessarily. (But I’m not a lawyer.)
Since one is (perhaps — I think the license text is ambiguous, see below) allowed to add additional permissions to the GPL and AGPL license, I could grant permissions to people in a way that they would not have to open source their whole WordPress installation.
Details: In both the AGPL and the GPL, there is a section 7 about Additional Terms. Those additional terms “supplement the terms of the AGPL/GPL license, by making exceptions from one or more of its conditions”.
It’s not okay to add further restrictions to the license, except in a few specific cases detailed in section 7 (e.g. regarding the disclaimer and author attributions).
It is, however, okay to add additional permissions (as far as I’ve understood, but I’m no lawyer). From section 7:
— I wonder what “which” in the last sentence refers back to. Does it refer to the material I add, or to the “covered work”?
If it refers to the material I add, to which I have copyright, then, if I give the appropriate permissions, I suppose people won’t have to open source their whole WP installation.