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Re: CUDA/OpenCL version of Octave for GPGPU?

From: Michael Poole
Subject: Re: CUDA/OpenCL version of Octave for GPGPU?
Date: Thu, 16 Jun 2011 13:58:35 -0400

2011/6/16 Jordi Gutiérrez Hermoso:
> On 16 June 2011 10:47, Michael Poole <address@hidden> wrote:
>> GPL'ed X clients use the same interface to talk to both open-source
>> and proprietary X drivers (whether for 2D, OpenGL, or other things),
>> so the GPL cannot reach across that interface.
> In my opinion, thinking if the "GPL can reach across an interface" is
> wrongheaded. The GPL isn't about interfaces, but about derived work.
> You may be able to argue that something is a derived work of GPLed
> software without mucking around with hair splitting if such and such
> technology is exchanging bytes in such and such way. Copyright law
> doesn't account for that level of detail about how a work is a derived
> work.

The protections that copyright law affords regarding derived works are
much more complicated than the point I was trying to make.  I did not
want to bring in the various legal criteria for derived works, or the
rules relating to derived works under various legal systems, because
it would confuse the discussion without changing the result.

If you think my statement was inaccurate, please explain in what way
some work could be a derived work of a GPL'ed work if the two works
have only a normal X11 client/server relationship.

>> OpenCL is a borderline case.  It has a standard interface for both API
>> and ABI,
> AIUI, OpenCL is only a specification like OpenGL, and any
> implementation of it may or may not be free. Is there already a
> standard implementation you're thinking of?

There is no standard implementation, and I do not know of any
conforming open source implementation, but the OpenCL specification
includes names for entry points and values for its named constants.  I
believe this means any conforming implementation of the specification
would be binary-compatible (and thus qualify OpenCL as a Standard
Interface under GPLv3), but I have not studied the compatibility issue
in great depth.

>> but it probably does not fall under the GPL's "system library"
>> exceptions on Linux on account of OpenCL libraries not being widely
>> distributed with Linux distributions. (There are reasonable
>> arguments that go both ways.) Ironically -- and unfortunately -- it
>> is probably more legitimate to distribute an OpenCL-linked GPL'ed
>> executable for Windows or Mac OS X than for any open source
>> operating system.
> The legitimacy of distributing non-free software isn't about legal
> technicalities. It's simply illegitimate because it prevents us, the
> users, from using, studying, and modifying the software to our needs.

Perhaps you misunderstand my point.  It is *probably* more legitimate
to distribute OpenCL GPL'ed executables on Windows and Mac OS because
the OpenCL libraries there would (I think) qualify as system
libraries.  That is unfortunate because the overall effect is to allow
more features to exist on non-free operating systems, while forbidding
those same features on operating systems that are mostly free.


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