[Qgis-developer] Plugin licence

[Vincent Picavet (ml)]

Hello,

On 25/05/2016 11:42, Tom Chadwin wrote:
> Vincent Picavet (ml) wrote
>> I may be wrong, but if qgis2web is like qgis2three, it generates
>> projects containing OL3 or leaflet code ?
>> In this case, there is no code link between the Python plugin and
>> Leaflet nor OL3
> 
> Yes, this is how it works. However, the code it generates *does* link to the
> other libraries in code. I think it would therefore be egregious to say no
> link exists between the Python code and the third-party JS libraries.

The term "link" is very subtle, and is key to the issue here. There is
absolutely no "link" in the sense of the GPL between your Python module
and the code you generate. The generated code can be considered as data
for your plugin ( template, replacement values).

For compiled code, the definition of a link is quite easy, and much more
complicated for script languages. The Plone project has done a deep
analysis some time ago and concluded that a "import" in Python is
considered a link in the sense of the GPL.

A grey area would be for example if you were using a QWebEngine
component in your Python Plugin, directly calling javascript functions
of the Javascript library from your Python code.
In that case I really do not know if it would be considered a link in
the GPL sense.

But for your use case with code generation it is really clear.

> Also, as I say, qgis2web redistributes those other libraries.
No problem neither, keep them with the original licence.

> I appreciate that, as you say, the other libs are largely licensed more
> permissively, and compatibly with QGIS - MIT/two-clause BSD.

Yes, this leads to much lesser complications.

> I guess I am just sceptical that GPL's requirement for GPL licensing of a
> product, purely by virtue of importing the first product as a library, is
> likely to hold much legal weight.
> 
> Anyway, to clarify, the advice is that GPLv2+ is the only acceptable licence
> - not even v3+?

As even noted, you could use a more permissive licence ( MIT, BSD ), but
the real use cases are rare.
As for using GPLv3 ( or later, which is the same right now ), it is more
complicated. QGIS being GPLv2+, it would be compatible. But you would
not be allowed to distribute that package ( QGIS & your GPLv3 plugin)
with any other piece of software which would be GPLv2 only, as GPLv2 and
GPLv3 are not compatible. Bad idea therefore.

Usual disclaimer : I'm not a lawyer, but still studied these issues a lot.

Vincent

> 
> Thanks for your patience and opinions
> 
> Tom
> 
> 
> 
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