Re: The purpose of the "license" list of a Guix package (Was: Re: Jam: which licence is this?)

[Leo Prikler]

Am Samstag, den 08.05.2021, 22:52 +0200 schrieb Maxime Devos:
> Leo Prikler schreef op za 08-05-2021 om 12:16 [+0200]:
> > [... something about dependencies and copyleft ...]
> > [...]
> > However, compliance is not *that* simple.  If you're dealing with
> > copyleft, providing the source is not enough, you also need to
> > license
> > your own work under that copyleft license, e.g. the GPL. [...]
> 
> Just checking if our understanding is the same, as I have seen a
> discussion on IRC where people the situation described below was
> _not_ legally acceptable.
Disclaimer: IANAL, but I'd argue the following.

> Suppose we have a GPLv3+ library, say guile-jwt.
> Suppose there is a (group of) developer(s) writing an application
> using guile-jwt. Let's call the application APP, and the developer(s)
> DEV.
At this point in time, I'd argue, that APP is "a work based on guile-
jwt", as defined in section 0 of the GPLv3.

> A hypothetical situation:
> 
>   * Suppose DEV is not very fond of licensing APP under a copyleft
> license,
>     and insteads prefers something with basically no licenses.
>   * DEV wants to choose, say, license:expat.
>   * license:expat is not license:gpl3
>   * Would this be a problem? I would think not. While APP used 
>     guile-jwt, it doesn't include or modify its source code.
I would think yes.  If what you said was true about Guile code, then
any proprietary code could just link against the GPL willy-nilly (well,
they'd have to take care to explicitly call dlopen, but you get the
point).  That obviously is not the case, the LGPL exists for a reason.

>     So I would think DEV must still respect GPL for the combination 
>     (e.g., if DEV provides binaries for APP, they must include source
>     code for guile-jwt *and* APP), and theoretically someone may fork
>     APP to replace guile-jwt with a hypothetical guile-jwt/expat, and
>     at that point the GPL doesn't apply anymore to the combination
>     APP-with-guile-jwt/expat.
I agree, that they'd at least have to provide the Corresponding Source
as laid out in section 6, but I also think they'd have to follow
section 4 and 5, in particular 5c.
The code within APP, that is not directly related to guile-jwt may very
well be Expat, and DEV might even go so far as to claim, that "just the
source" of the other stuff is Expat as well, but APP as a package must
be GPL'd (unless APP is only using public domain or Expat parts of
guile-jwt if they exist).

Once someone does have an expat-fork of guile-jwt and it's fair to no
longer assume APP to be based on guile-jwt, but rather guile-jwexpat,
the package as a whole can be distributed under the Expat license.

> I would find it interesting to know if some ‘legal people’ have
> worked out this situation.
Which ones?  The ones who tell you "you must form a bill of materials"
or the ones who tell you "just provide the source"?  :)

Regards,
Leo

PS: The above was written under the assumption, that you write your app
in a way, that it calls guile-jwt directly, not by forking guile and
communicating to it through pipes or sockets.