Re: [Discuss-gnuradio] GNURadio and GPL licensing issues

[Eric Blossom]

On Fri, Nov 19, 2004 at 10:34:39PM -0500, Krzysztof Kamieniecki wrote:
> From http://www.gnu.org/licenses/gpl-faq.html#MereAggregation
> <quote>
> By contrast, pipes, sockets and command-line arguments are communication 
> mechanisms normally used between two separate programs. So when they are 
> used for communication, the modules normally are separate programs. But 
> if the semantics of the communication are intimate enough, exchanging 
> complex internal data structures, that too could be a basis to consider 
> the two parts as combined into a larger program.
> <quote/>
> 
> My concern arises because of the statement "...But if the semantics of 
> the communication are intimate enough, exchanging complex internal data 
> structures, ..."
> 
> What does this mean in terms of GNURadio?
> 
> I believe there is a possibility of eventually having very complex 
> commands issued to a GPL SDR front end, so I'm hoping to get a consensus 
> on what limits comply with the "spirit" of GPL and the goals of GNURadio.

Here are my thoughts on the matter.  IANAL.

Our goal isn't to make GNU Radio unusable in a mixed free/non-free situation.

We DO want to make sure that the community developed code continues to
grow and improve, and that additional waveforms, etc are developed
under the GPL.

One way to think about this is by analogy to GCC.  GCC can be used
to develop non-free programs; the input and output of gcc are not
covered by the GPL.  Likewise, the input and output of GNU Radio are
not covered by the GPL.  For example, if someone used GNU Radio to
demodulate digital TV, the output of GNU Radio -- the MPEG transport
stream -- is not covered by the GPL.  Of course you may have other
problems with the output...

I don't see a problem with complex commands issued from some other
program.  The code that interprets the complex commands would be GPL.
The commands themselves wouldn't necessarily be, though this could be
a gray area.  Where it gets ugly is if the command is "Here's a bunch
of python code that implements my new proprietary foo-matic waveform.
Please run it for me."  On the other hand commands such as "set this
parameter", "get this value", "set waveform = FM", "send this
command to a USRP daughterboard" would be just fine.


Stuff that builds on the GNU Radio framework, such as new signal
processing blocks, would definitely be covered under the GPL.

As a first cut, if your code contains something like

  from gnuradio import gr

or

  #include <some gnuradio file>

then you are in GPL territory.



I'm sure this isn't the last word on this...

Eric