License issues for SkypeKit plugin

[John Bailey]

On 11/09/2012 07:03 PM, Daniel Muhra wrote:
<snip>
> 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)?

It's quite simple, actually.  Since Adium is GPL, and plugins are loaded into
Adium (i.e. not a separate process), the entire in-memory blob of executable
code becomes GPL in effect, regardless of what license you place your source
code under.  Linking with SkypeKit would cause that library to be loaded into
the same process, therefore making SkypeKit code GPL at runtime.  Not only does
this explicitly violate the SkypeKit license section you quote, some smart
lawyer could find a way to use that "it's GPL in memory!" argument to force
Microsoft to release SkypeKit source code, and depending on how it interacts
with Skype, potentially even Skype's source code.  Obviously, Microsoft isn't
going to be very happy about this.  Additionally, the MIT License is still an
Open Source license--it's even certified as such.  So is BSD.  So are a crapton
of other licenses.  Therefore any license which allows source code distribution
will violate the SkypeKit license.  It's going to be extremely difficult--in
fact, impossible--to make an Adium plugin that is not Open Source.

As far as Adium using Cocoa, Cocoa is exempt because it's a core system
component--it's not possible to have an OS X machine without that component.
Core system components are specifically exempted from falling under the GPL.

Now, theoretically it could be possible to get a GPL exemption for this, but
you'd also have to get an exemption from libpurple's developers and the
developers of all libpurple dependencies Adium uses.  This is a non-starter,
because as a developer (and therefore copyright holder) of libpurple, I refuse
to grant GPL exceptions for any purpose.  Even if you could get the exemption,
however, you would *still* be in violation of the SkypeKit license.

The bottom line here is it's impossible to develop an Adium plugin that can use
SkypeKit within the terms of SkypeKit's license, and the Adium guys are doing
the right thing by rejecting any plugin that uses SkypeKit.

John

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