[Adium-devl] GPL and Objective C

[Chris Forsythe]

It's not my fault that Jor-El sent me here :(

Although, Krypton never had Twinkies!


Colin Barrett wrote:

> 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
>>>>>>
>>>>>>