[Qemu-devel] Re: Sponsorship for QEMU Developers...

[Robert Wittams <robert@wittams.com>]

Leonardo E. Reiter wrote:
> Marc,
> 
> here is an easy link to use:
> 
> ftp://ftp.win4lin.com/pub/oss/
> 
> oss stands for Open Source Software of course.
> 
> the qemu tarball is a CVS head snapshot from the 2/20/05; mergepro.patch 
> gets applied to it to add our 3rd party stuff.  Basically what we do is 
> enable loading a dynamic shared object as a "plugin", and export symbols 
> back and forth as needed by supplying pointers to them both in vl.c and 
> in our plugin.  We do not use any additional header files or anything 
> like that in our closed source bits, since that would of course violate 
> the GPL.  We mainly did this so that we could "replace" the 
> initialization of certain built-in peripherals in QEMU with our own 
> proprietary versions that live in the plugin.  To date, we replace the 
> GUI ("display") and the IDE driver with our own home-grown versions. You 
> will notice that all QEMU structures are passed in as void pointers back 
> and forth, since we don't use any of the QEMU header files which define 
> them.  We instead get and set only the members we are interested in by 
> address in our plugin.
> 
> Note that this is fairly temporary.  We are working on making all of 
> QEMU a shared library object itself, and adding accessors (get/set) for 
> each QEMU structure type that are exported from the shared library. This 
> would encapsulate the GPL'd code in a much cleaner way, and would let us 
> avoid having to calculate addresses of members in our closed-source code 
> when getting or setting data from structures.
> 
> Let me know if you have any additional questions.
> 
> Best regards,
> 
> Leo Reiter

Erm... does this sound exactly like linking to anyone else? You can't 
honestly think that manually passing pointers around is going to be an 
end run around the GPL?

Leo, where did you get the idea that not using header files means that 
the combined system is not a derivative work? If the combined system is 
distributed with the GPLed work included, and relies on it to function, 
I see no way it can escape being considered a derived work and therefore 
GPL covered or undistributable.


Re your future plans:
A client of a GPLed library is considered a derivative work. That is 
Trolltechs entire business model, for chrissakes. Please read the GPL 
Faq at least.

-----------------------
http://www.gnu.org/licenses/gpl-faq.html#IfLibraryIsGPL
-----------------------
If a library is released under the GPL (not the LGPL), does that mean 
that any program which uses it has to be under the GPL?

     Yes, because the program as it is actually run includes the library.
-----------------------


If you have received Qemu under another licence (eg GPL + exceptions), 
please let the list know about it.

If not, you need to try to get it under another licence. If that fails, 
you need to find a way to run your proprietary code in a separate 
process - ie not linked to existing GPLed code.

I'm not a copyright holder on any portion of Qemu.... but this still 
concerns me.