Grout license feedback

[Morten Brørup]

> From: Robin Jarry [mailto:rjarry at redhat.com]
> Sent: Tuesday, 14 April 2026 11.27
> 
> Hi Morten,
> 
> Morten Brørup, Apr 14, 2026 at 10:54:
> > Hi Robin & Maxime,
> >
> > Having followed Grout progress on the sideline, I was taking a look
> at
> > it this morning, and the license struck me as unclear.
> >
> > As a fan of the BSD license, I have some feedback/questions.
> >
> > Please note: I'm not a license expert! Just happened to notice this,
> > and wanted to provide my thoughts.
> >
> > The README says that the project is BSD licensed, and only the FRR
> > plugin is GPL licensed.
> >
> > Doesn't the FRR plugin's GPL license "infect" the entire project?
> E.g.
> > if someone forks Grout, contributes some code to the new project and
> > distributes it as an executable, their project will be indirectly GPL
> > licensed - e.g. they must provide the complete source code of their
> > project - unless they remove the FRR plugin.
> >
> > Why the need to deviate from the BSD license?
> >
> > Assuming the FRR plugin is dynamically loadable, like a library,
> maybe
> > LGPL would be a better license than GPL?
> 
> That is a good question. FRR/zebra plugins are dlopen()ed by zebra at
> runtime. This makes dplane_grout.so automatically "infected" by the GPL
> license.
> 
> NB: Including headers from a GPL license project does *not* propagate
> the GPL license. The license is propagated only when code executes in
> the same memory space as GPL licensed code (e.g. via dynamic linking or
> dlopen).
> 
> However, dplane_grout.so is *not* linked against anything in grout. It
> just uses symbols from grout public API headers. The communication
> happens over a UNIX socket which does *not* propagate the GPL license.
> 
> So it is correct to have grout BSD licensed and the FRR plugin GPL
> licensed.

Thank you for the quick and detailed response, Robin.

I was confused, because I had missed an important point:
The FRR plugin is a "Grout connector" plugin to the FRR project, not a "FRR connector" plugin to the Grout project.

I suggest you mention that "for dummies" (like myself) under the License headline in the README file, where the GPL license is mentioned.

> 
> > Another detail: The Contribution Guidelines
> >
> [https://github.com/DPDK/grout/blob/1eb50571433d9a20378623012f4e0b750d1
> 60ec2/CONTRIBUTING.md]
> > say:
> >
> > "All contributions are made under the BSD-3-Clause license."
> >
> > You should update this to mention that contributions to the FRR
> plugin
> > are made under the GPL license. (Assuming you want to keep the plugin
> > GPL licensed.)
> 
> Indeed this should be updated. The contribution guidelines were written
> before we added the FRR plugin.
> 
> > PS: Looking forward to the next Grout presentations at the coming
> DPDK
> > Summit. J
> 
> Thanks, I'll be there!

Great. I haven't booked flight/hotel yet, but I expect to be there too. :-)

> 
> Cheers o/
> 
> Robin