Re: [libgpiod] consider changing the license of the C++ bindings

[Kent Gibson <warthog618@gmail.com>]

On Wed, Feb 12, 2020 at 11:00:56AM +0100, Bartosz Golaszewski wrote:
> śr., 12 lut 2020 o 08:48 Helmut Grohne <helmut.grohne@intenta.de> napisał(a):
> >
> > Hi,
> >
> > I've recently encountered libgpiod and found that its API is nice to
> > work with. Thank you for this piece of software.
> >
> > IANAL
> >
> > The library is licensed LGPL, which makes it available to non-free uses
> > in principle. For the C library, I think this is a good license. For the
> > C++ bindings, LGPL poses a little problem as code can be generated from
> > the header. For instance, libgpiodcxx is using `ctor() = default;`.
> > Strict intepretation of the LGPL would mean that a downstream user
> > should be able to recompile the whole product using libgpiodcxx.
> > Effectively, libgpiodcxx can be considered GPL (not LGPL) licensed for
> > practical purposes. You can find more background at:
> >  * https://blogs.msmvps.com/gdicanio/2016/07/11/the-lgpl-and-libraries-exposing-a-c-interface/
> >  * Eigen was initially LGPL and was converted to MPL2:
> >    https://eigen.tuxfamily.org/index.php?title=News:Relicensing_to_MPL2!
> >  * QT4 has also encountred this:
> >    https://lwn.net/Articles/315251/
> > I think that the LGPL when applied to C++ results in an unclear
> > licensing situation at best and an effective GPL at a strict
> > interpretation. Varying license interpretation rarely results in
> > anything good.
> >
> > For these reasons, I ask you to consider changing the license for
> > libgpiodcxx only (and not for libgpiod nor for the Python bindings). I
> > propose following Eigen and switching to MPL2. If however, the intention
> > is the strict reading of the non-lesser GPL, consider switching to that
> > instead. Either change improves the clarity of the licensing and makes
> > the intention visible.
> >
> 
> Hi Helmut,
> 
> thank you for this e-mail. I admit I'm not very well versed in
> software licensing. What you're saying makes sense and the links you
> posted seem to confirm it. I'll still try to get a second opinion on
> this. Anyway: my intention is to make the library available to
> non-free projects - including C++ bindings - so MPL2 makes sense.
> 
> There's only one significant contributor (new features, not bug-fixes)
> to C++ bindings other than me (Cc'ed Kent Gibson) from whom I'd need
> an ack on relicensing, so it shouldn't be very difficult to do.
> 

I agree with your intent, so feel free to relicense as you see fit.

Kent.

> While at it: LGPL is the only license used by all libgpiod components.
> Do you know if it makes sense to use regular GPL for programs that are
> part of the repo and LGPL for libraries only (except C++ bindings)?
> 
> Best regards,
> Bartosz Golaszewski