[Adium-devl] GPL and Objective C

[Evan Schoenberg]

The GPLv3 public committee meets at 5 PM EST on #comitteed  
(irc.freenode.net) on Tuesdays. Maybe that'd be a good contact point  
for getting in touch with someone connected with the GPL who could  
offer some sort of official response.

-Evan

On Mar 6, 2006, at 5:33 AM, Ofri Wolfus wrote:

> You're missing the most basic thing - you NEVER call a GPL code in a
> message. The system is the one that does or doesn't call it. It's
> completely out of your hands to decide what method implementation
> will be used by objc_msgSend(). I can even go one step further, and
> say that even if today my code results in a GPL function being
> called, in a future version of OS X it may not. You can not be held
> responsible for the decisions your computer makes, and therefor can
> not be blamed in calling GPL method imps.
>
> Finding these little holes in papers is what lawyers get paid for :-P
>
> - Ofri
>
> On 06/03/2006, at 02:05, Colin Barrett wrote:
>
>> Oh yeah? Well I wrote some awesome machine code out on a box of
>> punch cards, and it executes your JMP statements, so now I own all
>> *YOUR* stuff!
>>
>> You just can't beat little tiny holes in paper, man. You just can't.
>>
>> -Colin
>>
>> On Mar 5, 2006, at 5:16 PM, Adam Iser wrote:
>>
>>> I just wrote a block of assembly which JMPs into GPL code (A JMP
>>> is not
>>> a function call! HA! HA!).  All your GPL code are belong to me.
>>>
>>> - Adam
>>>
>>> Ofri Wolfus wrote:
>>>
>>>> Hi everyone,
>>>>
>>>> A discussion with David in IRC has lead me to talk with a friend of
>>>> mine (who is a lawyer) about the nature of objc code released under
>>>> GPL. As you probably know, a message to an object is translated by
>>>> the compiler to a call to one of the objc_msgSend() functions.
>>>> Therefor, you never get to call any 'real' function from your code
>>>> and you only indirectly call GPL functions.
>>>> Well, GPL code forbids you from linking to it unless your code is
>>>> GPL
>>>> as well, but what happens if the GPL code lives in a plugin  
>>>> which is
>>>> dynamically loaded? This is what GPL has to say about it (taken  
>>>> from
>>>> http://www.gnu.org/licenses/gpl-faq.html#GPLAndPlugins):
>>>>
>>>> "It depends on how the program invokes its plug-ins. If the program
>>>> uses fork and exec to invoke plug-ins, then the plug-ins are
>>>> separate
>>>> programs, so the license of the plug-in makes no requirements about
>>>> the main program.
>>>> If the program dynamically links plug-ins, and they make function
>>>> calls to each other and share data structures, we believe they
>>>> form a
>>>> single program, which must be treated as an extension of both the
>>>> main program and the plug-ins. In order to use the GPL-covered  
>>>> plug-
>>>> ins, the main program must be released under the GPL or a GPL-
>>>> compatible free software license, and that the terms of the GPL  
>>>> must
>>>> be followed when the main program is distributed for use with these
>>>> plug-ins.
>>>> If the program dynamically links plug-ins, but the communication
>>>> between them is limited to invoking the `main' function of the  
>>>> plug-
>>>> in with some options and waiting for it to return, that is a
>>>> borderline case."
>>>>
>>>> But message sending is not a function call... Therefor, a message
>>>> being sent to a GPL class, does not force the sender to be GPL as
>>>> well. As long as your code does not set instance variables of a GPL
>>>> class (directly - accessors are fine), use IMP caching or use the
>>>> @defs() directive, your code DOES NOT have to be released under GPL
>>>> license.
>>>>
>>>> But what about the classes themselves? GPL specifically says that
>>>> one
>>>> can not use GPL data structures in a non-GPL code. Well... it
>>>> doesn't
>>>> bother us at all since classes are translated by the compiler to  
>>>> the
>>>> objc_class struct which has no effect on us. The same goes with
>>>> instances of classes which are translated to pointers to an
>>>> objc_object struct.
>>>>
>>>> Quite revolutionary ha? ;-) Using plugins, commercial apps can take
>>>> advantage of ANY GPL code that can be wrapped in a cocoa class. Not
>>>> so good... But for us it also means some good stuff. It means that
>>>> Adium and ChatKit can use protocol libraries which are not GPL. :D
>>>>
>>>> - Ofri
>>>>
>>>>
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>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
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>>>
>>
>
>
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