LGPL 2.1 + GPL 3 = problems?

Philippe Verdy verdy_p at wanadoo.fr
Sun Jul 15 11:34:54 UTC 2007

> -----Message d'origine-----
> De : Arnoud Engelfriet [mailto:arnoud at engelfriet.net]
> Envoyé : dimanche 15 juillet 2007 13:04
> À : Philippe Verdy
> Cc : license-discuss at opensource.org
> Objet : Re: LGPL 2.1 + GPL 3 = problems?
> Philippe Verdy wrote:
> > Arnoud Engelfriet wrote:
> > > Yes, because the LGPLv3 allows conversion of the license to GPLv3.
> > > With that conversion you can comply with GPLv3 for the entire work.
> >
> > Wrong ! The LGPGL does NOT authorize the conversion of the licences
> covering
> > other necessary components. The terms that allows such promotion are
> those
> > found in the licences of those components.
> What I meant is that you can apply the terms of the GPL to any
> LGPL work instead of the LGPL terms. See LGPL 2 section 3, first sentence.

Wrong! Not any version of the GPL, unless otherwise specified in an
additional permission in the copyright notice of your library, or specified
explicitly in a later version of the ***LGPL*** (***and*** your library
specifies that it can be used according to a later version of the LGPL,
something that most LGPL libraries specify in their copyright notice).

For now this is not a problem because LGPLv3 explicitly allows using GPLv3,
so that a library originally licenced under LGPLv2.1 "or any later version"
can be used in a LGPLv3 library that can still used in a GPLv3 program, only
because the LGPLv2.1 permits using the terms of LGPLv3 that contains the
"additional permission" to the GPLv2...

But if the FSF publishes a GPLv3.1 update but no update to LGPLv3.0 to
authorize GPLv3.1, then you won't be able to use the LGLv3.0 library in a
GPLv3.1 program without either:

(1) Asking to the original author of the LGPLv3 library this additional
permission to convey your modified library using GPLv3.1 with an explicit
additional permission in your copyright notice like:

	"This library is free software: you can redistribute it and/or
	modify it under the terms of the GNU Lesser General Public License
	(LGPL) as published by the Free Software Foundation (FSF), either
	Version 3 of the License, or (at your option) any later version, or
	at your option) you may also use the terms of the GNU General Public
	License (GPL) version 3.1, as published by the FSF, or any later
	version of the GPL"
The last part "or any later version of the GPL" is optional, but may be used
only if the author has authorized it.

(2) Waiting for the FSF to publish a later version of the LGPL that allows
using the library within a GPL v3.1 program. Note that "or any later version
of the GPL" may be present absent from the updated LGPL v3.1, and if so, you
won't be able to include it in the copyright notice of your program without
asking for permission to the original author of the LGPL v3 library!

As both GPL v3.0 and LGPL v3.0 were published, this does not make any
problem for now. But it may happen with possible future versions of the
GPLv3, or with programs licenced by their original authors under GPLv3.0
with additional restrictions such as those excluding later versions of the

For now, all libraries licenced under LGPLv2.1 or LGPLv3.0 are compatible
with each other and with GPL 3.0 and GPL 3.1 programs, provided that GPL 3.0
programs and LGPL 3.0 libraries include the "any later version" statement in
their copyright notice, and you licence your combined works using at least
the highest version number of these component licences

You CANNOT distribute your combined work under the GPL v2.1 or LGPLv2.1 if
only one component is licenced under GPL v3.0 or LGPL v3, and this means
that the new section about the required extension of Patent Licencing in GPL
v3.0 will apply to your combined work.


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