linking BSD and GPL code via a plugin

[Johannes Buchner]

>Am 19.01.11, 09:45 -0500 schrieb Kevin Hunter:
>> Hello License List,
>>
>> I'm confused (yet again!) about linking to libraries and other programs. I 
>> am working with a BSD licensed project, and I've been tasked to write a 
>> plugin to call functions of a GPL project.
>>
>> - The project will distribute the plugin, but not the library against which 
>> the plugin links.
>>
>> - As I have currently instantiated the plugin, it sees if it can load the 
>> necessary libraries. If it can't, it disables itself.
>
>If the GPLed library is optional, the situation is much more relaxed.

A program (or library) that requires a GPL library to function must become GPL, even if the GPL library is not distributed. The only question to answer is can the program function without the GPL it depends on. If not, both form a single program.

See for example the GSL. 

Here are relevant FAQs:
http://www.gnu.org/licenses/gpl-faq.html#IfLibraryIsGPL
http://www.gnu.org/licenses/gpl-faq.html#LinkingWithGPL
http://www.gnu.org/licenses/gpl-faq.html#NFUseGPLPlugins

>From what you stated above, the plugin requires the GPL project, so it must be GPL (even if it doesn't come with the GPLed library).
However, the BSD project that just has a plugin API can probably work without this specific plugin, so it can remain BSD.

>> This will put the onus on the user to download and install the GPL library, 
>> which I thought was the point. 

This is something GPL libraries are fighting specifically. Here the hard dependency matters, not the form of distribution.

>>Then I saw this go by on another list:
>>
>> From another list:
>>> If they are linking to the [GPL] code or having Java code link to
>>> the [GPL'd] API then I believe there is a serious problem and the
>>> code that links to the GPL 3 code is then by definition covered by
>>> the GPL 3 license.
>
>Unlikely. Then someone can write a wrapper and turn all code into 
>GPL without any consent. Who would then to be blamed for what?
>
>The problem would be about distributing GPL and your BSD or 
>proprietary code, which must require the GPL code, side by side.

As stated above, not true.

>> I continue to be confused on this point (as do many others, given my 
>> googlings!). 

Start with reading the license, and material from GNU and FSF.

>>  Here is my understanding; please correct it inline as 
>> appropriate:
>>
>> I believe the issue is distribution. As long as $COMPANY does not 
>> _distribute_ GLPK along with their proprietary code, they *can* write to 
>> GLPK's API. Then, the onus is on the user to download and install the GLPK. 
>> If the user decides to use GLPK for their own internal uses, there is no 
>> problem. Since $COMPANY is not distributing the GPL code, all is well.
>>
>> Have I blubbed that point?
>
>Seems fine to my personal not lawyerish view.



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