License issues for SkypeKit plugin

[Graham Booker]

Plugins need not be strictly GPL, but they must be GPL compatible: http://www.gnu.org/licenses/gpl-faq.html#GPLAndPlugins

It looks like there is no issue with you making a plugin that is MIT licensed, so long as the GPL is followed in distribution (such as making the source code available).  The question is that of the library.  The license quoted below states that "no portion of the product shall contain any Open Source Software…."  I read this as no part of the product can be open source.  While I would assert that this is a stupid requirement, it seems to mean that your MIT licensed code cannot be part of the product.  If the intent of the license was what you believe, then leaving out the Open Source Software portion will still achieve it.

Now there is a way around this that can work.  You split the plugin into two parts.  One links with Adium as a plugin, and it is under a GPL compatible license.  The second is not open source (to satisfy the SkypeKit license only), and links with the library.  The first launches the second as a separate program via fork/exec.  The two communicate over a socket protocol, pipe, or some other means.  You may be able to use Distributed Objects, but that's a bit of a grey area.  Technically it is RPC and not sharing of objects, so it should be fine.  Communication between two programs over a socket or pipe is one of the recommended means of getting around this restriction, so going that route should have no issues.

Yes, this is a royal pain, but this is the price imposed by the GPL.  This demonstrates exactly why we went through all the trouble to relicense Perian as LGPL in it's early stages (by getting everyone's approval to do so and by compiling FFmpeg without enabling GPL code).

On Nov 9, 2012, at 6:16 PM, David Smith wrote:

> I am also not a lawyer, but my understanding is that the GPL specifically exempts system libraries, with the intent of allowing open source software to run on closed source or partially closed source OSs. Things linking against Adium are, for better or worse, required to be GPL-licensed.
> 
> 	David
> 
> On Nov 9, 2012, at 4:03 PM, Daniel Muhra <daniel.muhra at googlemail.com> wrote:
> 
>> Hi,
>> 
>> I developed a SkypeKit plugin for Adium that I wanted to release on AdiumXtras. Unfortunately it was rejected with the remark, that SkypeKit's license would not allow it to use it within an open source product. Apparently the cited paragraph would be the following:
>> 
>> 10.1.5. 
>> No portion of the SkypeKit Product contains or shall contain any Open Source Software or any other software that could interfere with or compromise Skype's Intellectual Property Rights in the SkypeKit or which may require you or Skype to disclose any source code included in the SkypeKit.
>> 
>> From my understanding, this does not imply Open Source Software in general, but only those, which would e.g. force you to provide the source code for the SkypeKit library. My code uses the MIT license so I see no implication for the SkypeKit library and thereby I should be safe.
>> The only part I have doubts about is the fact, that my plugin uses SkypeKit and since Adium uses the GPL, Adium plugins need to be fully GPL compatible too. I'm not really sure what this means in terms of dependencies, but on the other hand, Adium itself is based on Cocoa which is definitely not using a GPL compatible license...
>> 
>> Has anyone here any thoughts on this (including some explanation)?
>> 
>> Cheers,
>> Daniel
> 


- Graham


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