Dual licensing with two copyleft licenses

[John Cowan]

Evan Prodromou scripsit:

> My understanding, then, is that Bob must choose one or the other license
> offered by Alice. Since both of these licenses require derivative works
> to be licensed identically, Bob's derivative work must have the same
> license as the one he chose to use.

I agree with your reasoning.

> P.S. I believe there may be other ways that Bob and Alice can make
> arrangements so that the derivative work Bob made can be dual-licensed,
> too. Assignment of copyright by Bob to Alice is one way, for example.

Another way would be for Alice to grant the right to dual-license by
a special exception, more or less like this:

	As a special exception, <LICENSOR> gives permission for
	additional uses of the text contained in its release of
	<PROGRAM>.

	The exception is that you may dual-license any derivative
	works under both <LICENSEA> and <LICENSEB> simultaneously,
	notwithstanding any statements in either <LICENSEA> or
	<LICENSEB> to the contrary.

	This exception does not excuse you from compliance with
	any other terms of either <LICENSEA> or <LICENSEB>.

(I adapted this text from the license of Guile.)

Since the exception merely gives you additional rights, it cannot
affect the Free and Open Source status of <PROGRAM>.

-- 
A witness cannot give evidence of his           John Cowan
age unless he can remember being born.          jcowan at reutershealth.com
  --Judge Blagden                               http://www.ccil.org/~cowan