[LAD] GPL and plugins

Paul Davis paul at linuxaudiosystems.com
Tue Jun 22 00:27:57 UTC 2010


On Mon, Jun 21, 2010 at 8:21 PM, Albert Graef <Dr.Graef at t-online.de> wrote:

> Yes. IANAL and all that, but the GPL is very clear on that, see e.g.:
> http://www.gnu.org/licenses/gpl-faq.html#GPLPluginsInNF

i would hardly call this "very clear"
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Can I release a non-free program that's designed to load a GPL-covered plug-in?

If [ ... ] ***WE BELIEVE*** they form a single program, which must be
treated as an extension of both the main program and the plug-ins. In
order to use the GPL-covered plug-ins, the main program must be
released under the GPL or a GPL-compatible free software license, and
that the terms of the GPL must be followed when the main program is
distributed for use with these plug-ins.

If the program dynamically links plug-ins, but the communication
between them is limited to invoking the ‘main’ function of the plug-in
with some options and waiting for it to return, that ***IS A
BORDERLINE CASE***.
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(emphasis added)

> In fact, library authors decidedly use the GPL (rather than the LGPL
> which allows linking against proprietary software) to prevent
> unsolicited use of their libraries in commercial software.

i don't believe that this is really the same thing. yes, this
definitely the point of releasing a library under the GPL. but
libraries are not plugins. They do not supply an API, they use one.
plugins are derivatives of a plugin API (which may also be a library),
just as hosts might be. that doesn't make hosts derivatives of the
plugins, which is quite different to the situation where a program
(even a host) uses a library in a more traditional way.

maybe the mathematical formulation is: is derivation distributive? or
have i even forgotten that much of my high school math?



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