[Adium-devl] GPL and Objective C

[Colin Barrett]

Man, you broke the chain of progressively less simple technology :(

-Colin

On Mar 5, 2006, at 7:23 PM, Chris Forsythe wrote:

> I am Kal-El. I used my heat vision to destroy your code. I froze your
> punch cards with my breath, and threw them into the orbit of  
> Jupiter. I
> have crushed your punch card reader with my bare hands.
>
> I now own ALL your stuff!
>
> Kal-El
>
> Augie Fackler wrote:
>
>> I'm wiring up my own reader with vacuum tubes for reading your punch
>> cards and storing their code to my hard drive, so all your punch
>> cards are belong to me.
>>
>> On Mar 5, 2006, at 7:05 PM, 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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