[Adium-devl] GPL and Objective C

[Chris Forsythe]

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