[development] Modules that integrate non-GPL PHP apps violate the GPL.

[Thomas Barregren]

ttw+drupal at cobbled.net skrev:
> On 31.08-17:52, Thomas Barregren wrote:
> [ ... ]
>   
>>>> The issue original brought up by Jeff Eaton was about the fact that 
>>>> it is not permissible to write modules that bridge software with a 
>>>> license not compatible with GPL.
>>>>         
> [ ... ]
>   
>> You surprise me. GPL has been around for *18 years* and this reciprocity 
>> (a.k.a. "copyleft") is the very heart of the license.
>>     
> [ ... ]
>   
>> Wrong. You are allowed to integrate GPL-application with any non-GPL 
>> application.
>>     
>
> i believe you contradict yourself.  the issue is the extension of GPL
> to include interfacing software, as below
>   

No, I don't contradict myself. :-)

The first snippet was meant to bring the discussion back to the original 
issue: what regulations applies to a module that tries to bridge GPLed 
code with non-GPLed code. I was a little careless in my choice of words. 
I should have written "distribute" instead of "write". Thus, the correct 
wording should have been: "The issue original brought up by Jeff Eaton 
was about the fact that  it is not permissible to *distribute* modules 
that bridge software with a  license not compatible with GPL."

The third snippet states a fact. You are allowed to integrate 
GPL-application with any non-GPL application. I could perhaps have added 
that this right doesn't imply a right to also distribute the resulting 
derived work. But I didn't, because I thought it is a corollary of the  
following paragraph in my answer (which you didn't quote).

I don't understand what the second snippet has to d with my alleged 
contradiction.


> [ ... ]
>   
>>>>   * to study and modify the program.
>>>>         
>>> --unless, of course, you want to bridge it with a non-GPL application, 
>>> apparently.
>>>       
>> Wrong. You are allowed to study and modify the program for any reason, 
>> including for the purpose of bridging it with non-GPL application.
>>     
> [ ... ]
>   
>>>> So, to solve the problem that the licensing of Drupal currently force 
>>>> us to "dumbing down" or "bypassing of established application 
>>>> methodologies", I suggest that the Drupal licensing is supplemented 
>>>> with an exception for module developers linking through hooks.
>>>>         
>
> if you are allowed to study and modify the program for the purpose of
> bridging it with non-GPL code then there is no cross pollination of
> the licenses.  this has traditionally been done (i.e.  the use of
> GPL'd header files in compilation) but often brought under question
> by more aggressive GPL proponents.
>   

You are allowed to study and modify the program as much as you want. No 
GPL proponents, aggressive or not, say something else (if they know what 
they are talking about).

But, to *distribute* the derived work, you must license the derived work 
under GPL. If you cannot do that, for instance because you have 
integrated code under a license not compatible with GPL, you are not 
allowed to distribute it. But you may still use it.

> i think the original author is confused about the exact status of GPL,
> especially, in relation to something like hooks where, it would appear
> to me, there is no issue.  essentially, i see no reason you could not
> interface an application using hooks and keep that application
> propiertory.
Generally, you cannot "interface an application using hooks and keep 
that application propiertory" as explained here:

  http://www.gnu.org/licenses/old-licenses/gpl-2.0-faq.html#MoneyGuzzlerInc

But, as this discussion is about, this can also pose a hindrance for 
situations where it can seem reasonable to include software with license 
not compatible with GPL.

For an example, imagine someone who has put in a lot of effort to write 
code that integrates a popular but proprietary software with Drupal. So 
far it is okay under GPL. But now he wants to share his effort with the 
community. Since the integration code calls functions and share data 
structures with both the proprietary software and Drupal, it is not 
allowed.

Fortunately, there is a solution. As long as you don't revoke any rights 
granted by GPL, you can add your own terms and conditions. This can be 
used to allow integration with software under a license incompatible 
with GPL. Two examples on this:

 * 
http://www.gnu.org/licenses/old-licenses/gpl-2.0-faq.html#GPLIncompatibleLibs 

 * 
http://www.gnu.org/licenses/old-licenses/gpl-2.0-faq.html#LinkingOverControlledInterface 


So, to solve the problem with bridging modules integrating 3rd party 
integration,

    I suggest that the Drupal licensing is supplemented with an
    exception for module developers linking through hooks.


Best regards,
Thomas