LGPL library using only LGPL-parts of partially GPL shared library (gnutls, nettle)

Simon Josefsson simon at josefsson.org
Sun Feb 20 21:31:39 CET 2011

Simon Josefsson <simon at josefsson.org> writes:

> Andreas Metzler <ametzler at downhill.at.eu.org> writes:
>> On 2011-02-20 Simon Josefsson <simon at josefsson.org> wrote:
>>> Andreas Metzler <ametzler at downhill.at.eu.org> writes:
>> [...]
>>> > I have the feeling that the discussion I started is an academic one
>>> > anyway. Nettle's public key library (libhogweed) uses and links against
>>> > libgmp, which is LGPLv3+. Therefore switching gnutls from gcrypt to
>>> > nettle would break GPLv2-compatibility (GPLv2 without the "or any
>>> > later version " clause). Oh dear.
>>> It has been discussed to dual-license some libraries under
>>> GPLv2+/LGPLv3+ to avoid this problem.  I wonder if this could be a way
>>> out here.  GnuTLS 2.12 is not released (and there is not even any
>>> release candidates), so we still have time to resolve this in a good
>>> way.
>> [...]
>> Hello,
>> Afaik there is nothing GnuTLS can do. It is using the most permissive
>> license of the involved packages. The culprit is the combination of
>> third party (L)GPL-v2only software (e.g. cups) with libgmp, which
>> switched from LGPLv2+ to LGPLv3+ in 4.2.2.
> The FSF has clarified that to resolve that problem, it is recommended to
> dual-license projects under GPLv2+/LGPLv3+ see:
> http://www.gnu.org/prep/maintain/maintain.html#Licensing-of-GNU-Packages
> So if GMP follows this suggestion, the problem would be resolved for
> GPLv2-only projects.  Did you really notice any LGPLv2-only projects
> using GnuTLS when you looked?

I now realize that LGPLv2-only projects is not a problem since
LGPLv2-only can be upgraded to GPLv2 which would then be
GPLv2-compatible again.

So let me rephrase the question: is there any project that happen to
combine LGPLv2-only and GPLv2+-incompatible licensed code?  Only such a
project would be problematic even if GMP would become dual licensed
under GPLv2+/LGPLv3+.  If we can get any kind of metrics on the scale of
this problem, we can think about whether it is a problem worth solving.


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