Dual licensing

[Rick Moen]

Quoting Marius Amado Alves (amado.alves at netcabo.pt):

> >The spirit of Open Source is to allow the downstream distributors to
> >distribute however they like, without restriction. *Any* restriction.
> 
> Why are the other conditions e.g. the requirement to distribute under 
> the same license (GPL) not considered "restrictions"?

The GPL (and MPL, LGPL, Arpic, Affero, etc.) licences' copyleft
obligations have historically annoyed a number of open source people:
They're of course free to eschew (and replace using the sweat of their
own brows) affected code -- a quite honourable choice taken, for
example, by the OpenBSD Foundation in removing copylefted modules from
what became OpenSSH.

I would guess that consensus classes those licences' copyleft provisions
as fair play and easily within the province of open source because the
reciprocity required is no more than what the original developer did --
availability of your source under the same terms if you've released
derivatives in public -- and because those provisions otherwise don't
restrict the rights to fork, use, derive, or redistribute in any way.

(In other words, saying "any restriction" is an over-simplification.
Nobody serious alleges that the Apache licence isn't open source just
because it includes a clause protecting the Apache Foundation's
trademarks, even though that's a "restriction" of the licenced code --
because the substantive rights that the concept open source entails are
unaffected.)


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