Dual licensing with two copyleft licenses

[Evan Prodromou]

On Fri, 2004-03-12 at 10:33 -0800, Chad.Woodford at windriver.com wrote:

> I think the confusion here can be cleared up by noticing that Originator has
> created a single work available under both license A and license B (both of
> which allow for modifications of course).

To be precise: almost all dual-licensing makes the work available under
license A OR license B. Making a work available under license A AND
license B very rarely makes sense -- the wording of most licenses is
such that they don't combine well, and some have conflicting
requirements. I'm not saying its impossible, but I think that most
real-world licenses don't allow for an AND relationship.

> Then, Contributor1 has come along
> and made some modifications.  Contributor1 owns those modifications.
> Contributor1 then announces that s/he is licensing the modifications under
> both A and B.

Sound the trumpets! B-) 

Seriously, though it's important to remember that Contributor doesn't
have free rein in deciding how his/her modifications are licensed.
Copyright law gives the Originator considerable say in how derivative
works are published. Unless Contributor1's contributions are
sufficiently independent to be a standalone copyrightable work, s/he is
subject to Originator's whims about licensing.

This is, after all, why and how copyleft works.

> Because the downstream contributor is never changing or
> adding to either license, it does not matter that one of the licenses
> forbids dual licensing, etc., or even that some licenses treat the
> contributor as a sublicensee of the previous contributor and some treat the
> contributor as a licensee of all the previous (c) owners.
> 
> Does that make sense?

I'm afraid not. If neither license allows dual-licensing derivative
works, I have a hard time seeing how the alternation between them does.

~ESP

-- 
Evan Prodromou                  .O.
http://bad.dynu.ca/~evan/       ..O
evan at bad.dynu.ca                OOO