[QGIS-Developer] license requirements for QGIS plugin

[Luigi Pirelli]

On 6 March 2018 at 05:14, Olivier Dalang <olivier.dalang at gmail.com> wrote:
> Then, I found this [3] saying it's possible to use closed external tools,
> such as file based exchanges from/to external applications.

yes, it does not violate GPL calling external executable

> So if they build a GPL-licensed plugin calling a proprietary executable, how
> external would that latter executable need to be to comply to GPL ?
> - could it be shipped with the plugin, in the plugin repo ?

No, for two reasons.
1) no executable blobs are allowed in the main qgis plugin repo
2) should match executable redistribution policy of the executable

btw you can setup you own repo to distribute you plugin with executable blobs.
Here for example a plugin repo with a single plugin with a executabel
blob inside:
https://github.com/QTrafficmodel/QTrafficPluginRepository

> - if not, could it be dynamically downloaded by the plugin in the background?

Yes. I suggest to do it explicitly asking user permission and ask for
license agreement.

> - if not, could it be downloaded by the plugin with some kind of user
> interaction (e.g. copy/paste a link) ?

Yes

> - if not, could it be manually downloaded by the user and placed somewhere ?

yes

> And then, as far as I understand GPL-2, the requirements only apply when you
> distribute the software, which means you can keep all the code for yourself.

AFAIK GPL2 is always applied, not only for distribution. It's a
Copyright => it's an author right.

> When is it considered that the software is distributed ?
> - if they distribute it only to users inside their organization ?
> - if they distribute it only to users from partner organizations ?
> - if it's not considered distributed when it's done only internally, can
> they have internal agreements to prevent internal users from distributing
> the software ?

I leave these unanswered... because it's a complex argument.

My experience is that:
1) commtter of a work have the right to access source code
2) publication have to be negotiated with committer (btw because it's
a GPL would be "fair" to have it published by default)
3) Internal agreement are commonly (and sadly if related with GPL)
used to avoid distribution.

for sure the argument is much more complex than here exposed.

>
> Thank you very much in advance for these clarifications !
>
> And sorry if this is not the best place to ask basic GPL questions... But
> the topic is very complex, and it seems integrating GPL/propritery software
> is always an edge case. Maybe we could add some vulgarized information about
> this in the pyqgis cookbook ?
>
> Kind regards,
>
> Olivier
>
>
> [1] http://blog.qgis.org/2016/05/29/licensing-requirements-for-qgis-plugins/
> [2]
> https://www.gnu.org/licenses/old-licenses/gpl-2.0-faq.en.html#GPLAndPlugins
> [3] https://gis.stackexchange.com/a/61069


Luigi Pirelli

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