[Product-Developers] Non-open source plone plugins?

Guido Stevens guido.stevens at cosent.net
Wed Jul 31 13:59:18 UTC 2013

On 31/07/13 14:42, Héctor Velarde wrote:
> On 31/07/13 04:03, Dylan Jay wrote:
>> My understand was that you couldn't license a plone product with
>> anything other than a GPL license due to the Plone GPL license. Does
>> that prevent you from being to sell a plugin and not publish the
>> plugin on pypi or plone.org?
> HV> I just take a look at the GPL and I have a different interpretation
> (as with anything involving lawyers):
> "These requirements [the conditions to distribute a modified copy of the
> Program] apply to the modified work as a whole. If identifiable sections
> of that work are not derived from the Program, and can be reasonably
> considered independent and separate works in themselves,

That clause is key. In tech-speak, not lawyerese, that normally means 
that your proprietary plugin must be able to run standalone, or against 
a compatible interface that is not Plone. If you write a plugin that can 
only be used as part of a Plone installation, I'd consider that a 
derived work that ought to be released under a GPLv2-compatible license.

One can work around that by splitting the package into a "standalone" 
proprietary core logic module that does not require Plone, and a second 
GPLv2 plone integration module that requires both Plone and the 
proprietary work.

> we license some Plone packages with licenses different from GPLv2, like MIT

The situation is different for utilities which are required *by* Plone, 
than it is for plugins that require Plone. utility <- Plone <- plugin


PS note what was said earlier: there's no requirement to publish a GPLv2 
derived work to the world. Giving the customer GPLv2 code + rights is 

     Guido Stevens  |  +31.43.3618933  |  http://cosent.nl

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