If a program released under the GPL uses plug-ins, what are the
requirements for the licenses of a plug-in?
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It depends on how the program invokes its plug-ins. If the program
uses fork and exec to invoke plug-ins, then the plug-ins are separate
programs, so the license for the main program makes no requirements
for them.
If the program dynamically links plug-ins, and they make function
calls to each other and share data structures, we believe they form a
single program, which must be treated as an extension of both the main
program and the plug-ins. This means the plug-ins must be released
under the GPL or a GPL-compatible free software license, and that the
terms of the GPL must be followed when those plug-ins are distributed.
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.
Наш случай - третий абзац.
Хотя прямого ответа в нем и нет, но мне думается что в этом случае
подходит вот это:
Can I write free software that uses non-free libraries?
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If the program is already written using the non-free library, perhaps
it is too late to change the decision. You may as well release the
program as it stands, rather than not release it. But please mention
in the README that the need for the non-free library is a drawback,
and suggest the task of changing the program so that it does the same
job without the non-free library. Please suggest that anyone who
thinks of doing substantial further work on the program first free it
from dependence on the non-free library.
Что кратко переводится как "ну пожалуйста пожалуйста не надо".
[...]
Далее, вот там -
http://www.gnu.org/licenses/gpl-faq.html#GPLAndPlugins, не менее прямо
классифицируются три случая взаимосвязи GPL программы и non-GPL
библиотеки. Я приводил этот текст в предыдущем письме.
В нашем случае, это "that is a borderline case" между " license for
the main program makes no requirements for them" и " the plug-ins must
be released under the GPL". Иными словами, авторы GPL сами не знают,
что в этом случае следует делать D)