On Tue, 2010-12-28 at 09:30 -0800, Brian Gerkey wrote: 
> On Thu, Nov 4, 2010 at 12:54 PM, Mrinal Kalakrishnan <mail@mrinal.net> wrote:
> > Does anyone know the implications of a GPL-licensed .msg or .srv file?
> > If I wrote code that uses these messages (through the generated C++
> > code), does my code also need to be under the GPL? Or maybe, because
> > the code generation process only reads the GPL-encumbered .msg file
> > and outputs independent C++ code it's somehow free of the license?
> 
> Blaise answered earlier regarding the inclusion of GPL-licensed headers.
> 
> As the question of whether the headers produced from GPL-licensed .msg
> files are indeed GPL-licensed, I would say that the answer is
> probably, yes.  An item from the GPL FAQ
> (http://www.gnu.org/licenses/gpl-faq.html#GPLOutput) includes the
> following advice:
> 
> "More generally, when a program translates its input into some other
> form, the copyright status of the output inherits that of the input it
> was generated from."

If this is the case, I think this deserves a warning on the wiki, and
encouragement that the .msg, .srv, etc are BSD licensed or public
domain.