Re: Overview of copyright issues

[Joseph Wakeling]

Hans Aberg wrote:
> You might check with the GNUers if it is the intention. It means that
> sources can be tivoized, even in the face of the new v3.

It's GPLv2, and not the 'or later', that allows for tivoization -- but
you have to question whether this is a serious risk for Lilypond.

> Linking is always allowed if you make sure the interfaces are provided
> and other linking info is provided - copyright only controls
> distribution of the parts that makes it creatively unique, and v3 seemed
> to have changed over v2 to bring that out. There is no legal requirement
> that the parts should have the same license.

The parts need a compatible license if one links to the other.  GPLv2
and GPLv3 are not compatible licenses.  That's why the 'or later' is
important -- it allows that compatibility.

> But it has the effect that sources that formerly have been OK to
> distribute may not be so. For example, if they are tivoized, then when
> the GPL v3 now has arrived, the old sources cannot be tivoized, even if
> the package itself has not been changed.
> 
> On the other hand, the formulation "or later" means that new sources can
> be tivoized even if the new version v3 has been released, unless they
> explicitly mention v3.

Again, the 'or later' has nothing to do with tivoization.  It's GPLv2
that allows for that possibility (which, again, is not likely).

If Lilypond does switch to GPLv3 I would strongly argue for a 'GPLv3 or
later' formulation, to avoid this problem arising again if a further GPL
revision is released.

I don't think it matters much whether Lilypond moves to GPLv3 because
most of the risks that GPLv3 is designed to obviate are unlikely to
arise in the case of Lilypond.  I _do_ think it matters that Lilypond be
released under license terms that are compatible with GPLv3 and future
potential releases of the GPL.