Re: LGPL-library (tntdb) linked with GPL-library (mysql)
On 8/26/06, Francesco Poli <frx@firenze.linux.it> wrote:
On Sat, 26 Aug 2006 14:18:00 +0300 Markus Laire wrote:
> On 8/26/06, Don Armstrong <don@debian.org> wrote:
> > On Sat, 26 Aug 2006, Markus Laire wrote:
[...]
> > > Because according to your interpretation I would be able to use
> > > *any* GPL:ed library using the terms of LGPL with this simple
> > > trick:
> >
> > You are misunderstanding my interpretation.
> >
> > > 1. Take a GPL:ed library
> > > 2. Create LGPL:ed library which uses the GPL:ed library, and
> > > offers the exact same functionality.
> > > 3. Use the created LGPL:ed library instead of the original one, to
> > > get exact same functionality without (some) restrictions of the
> > > GPL.
> >
> > This requires complying with the GPL because you are creating a
> > derivative work of the GPLed work.
>
> But isn't this exactly what the original poster asked: Can you LGPL a
> program (tntdb) which links with GPL:ed program (mysql)?
No, the original poster asked if the *copyright holder* of a work
(tntdb), which links with a GPLed work (mysql), can change the license
of his own work (tntdb) to LGPL, and still create a distributable (by
other people) binary package!
Since he's the copyright holder, he can choose any license he likes, of
course.
The issue is: will the resulting binary package be distributable by
other people?
Assuming (to be on the safe side) that the FSF's legal theory on linking
is true: when you distribute tntdb in binary form linked against GPLed
mysql, you must make the source code for both available under the GPL.
Hence, the question rises: would an LGPLed tntdb be available under the
GPL?
And the answer is: yes, because of the explicit LGPL->GPL conversion
clause found in the LGPL (and quoted by Don Armstrong). Any work under
the LGPL is effectively available under the GPL too (but the reverse is
not true!).
So LGPLed tntdb would be *distributable* by others.
But would it be *usable* by others in his/her own program under the
LGPL license?
If yes, then he/she would effectively also be using mysql under the
LGPL license, which IMHO is not possible.
If no, then why would the author want to use LGPL if nobody can use
the tntdb under that license?
No, I don't think that Don Armstrong's answer was wrong. A bit
summarized, perhaps, but not wrong.
I hope I have somewhat clarified... :p
If you are saying that LGPL:ed tntdb would be distributable as long as
nobody uses it under the LGPL license, but only under the GPL license,
then I think I do understand.
But I think that the original poster wanted to allow usage of tntdb
under the LGPL license (why else would he want to use that license)
and IMHO that is not possible because it links with GPLed mysql.
--
Markus Laire
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