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Re: Question regarding QPLed plugins for a GPLed app

In message <[🔎] 20050317044922.GB953@eclipse.debian.net>, Ben Burton <bab@debian.org> writes

I'm currently involved in a discussion on kde-core-devel regarding the
use of a QPLed plugin that is dlopened within a GPLed application.  For


I received the following response, claiming that dlopened plugins do not
need to be GPL-compatible:

> Given that the QPL is GPL-incompatible, this raises issues for GPLed
> programs that wish to use this kpart.  I believe this at least
> includes quanta and kdevelop (unless I'm mistaken).

kparts are loaded at runtime. It has always been understood in the
community that the license restrictions based on copyright law do not
apply to runtime components. The implications of reinterpreting USC 17
this way are profound. The effects on Java development alone would be

It is somewhat understood that a deliberate misuse of runtime components
to circumvent copyrights is not allowed, but this is certainly NOT the
case for quanta and kdevelop (you also forgot konqueror). These
applications are designed to load available runtime components solely
on the basis of the services made available. There is no copyright
violation occuring when a user loads a plugin at runtime, particularly
one with a generic interface like a kpart.

Given that the GPL explicitly does not cover use of the software, and permits use as required, I would say it's definitely the case that no copyright violation occurs when the user loads the component. Assuming the main app is GPL, and the plug-in is QPL, the user has legal possession of both and therefore the GPL permits their use.

I'd appreciate if debian-legal could offer their advice here as to
whether this situation is allowable or not.

I'm assuming the main app looks in a standard directory for plug-ins, and has a standard means of querying the plug-in to find out what it does. Provided the main app has no prior knowledge of that particular plug-in, I'd say that the main app is an independent work separate from the plug-in.

Indeed, while I will be using the LGPL (where this sort of thing doesn't matter), as and when I get round to writing the app I'm working on I intend to use exactly this technique as a means of separating code and dealing with licensing issues.

Okay, so the main app is independent of the plug-in. The next question is whether the plug-in is separate from the main app. How much does the plug-in know about the main app? Are you only using header files (which aren't copyrightable)? Are you linking to any of the main app's libraries!? How much does your makefile know about the main app?

Those are the crucial questions, as they determine whether the main app's GPL spills over and infects the plug-in. In which case, it becomes a copyright violation if you distribute the plug-in as anything other than GPL.

Please CC me on replies; I'm not subscribed.

Thanks - Ben.

Anthony W. Youngman - wol at thewolery dot demon dot co dot uk
HEX wondered how much he should tell the Wizards. He felt it would not be a
good idea to burden them with too much input. Hex always thought of his reports
as Lies-to-People.
The Science of Discworld : (c) Terry Pratchett 1999

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