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Re: ELPA license, LGPL + additional restrictions



On Sat, 3 Nov 2012 20:31:57 +0100 Michael Banck wrote:

[...]
> After thinking about this some more, I guess their fear might be that
> people modify and redistribute their ELPA library as part of a bigger
> GPL project.

It's possible...

> As the LGPL->GPL relicensing seems to be a one-way street,

It is my understanding that the conversion is indeed one-way.

> they might understandably think that they will not be able to
> incorporate those GPL'd modifications into their version.

I think that this is correct, but disabling the one-way convertibility
to GPL destroys the compatibility with the GPL itself, thus making the
ELPA library unacceptable for *any* project where *any* part or other
library is GPL-licensed. That's a fairly large number of projects,
I guess!

> 
> Is this a valid concern and if so, is there some way around it?

I think the only way around it is adopting the GNU LGPL without any
additional clauses and relying on people's goodwill to contribute back
modifications under the same licensing terms (even though it would be
legally possible to redistribute GPL-licensed modifications, that
could not be incorporated back under the LGPL).

Another strategy could be to adopt the GNU (ordinary) GPL for the ELPA
library. This would have the effect to forbid linking with non-free
works (or even with free, but GPL-incompatible works), but any
published modification would be guaranteed to be incorporable into the
official ELPA library.
Well, unless someone plays with the "or later" mechanism: I mean, a
work released under the terms of the GNU GPL v2 or later can be
modified and mixed with code available under the GNU GPL v3 or later;
this modification cannot be incorporated back into the original work,
unless you can live with the fact that the original work effectively
becomes licensed under the terms of the GNU GPL v3 or later (thus losing
GPLv2-compatibility). In order to avoid this, one would have to license
under the GNU GPL v3 only (thus losing GPLv2-compatibility upfront) or
otherwise under the GNU GPL v2 only (thus losing GPLv3-compatibility
upfront)...



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