Dual licensing with two copyleft licenses

[Brian Behlendorf]

On Thu, 2 Dec 2004, Evan Prodromou wrote:
> Well, that's a good question. As I see it, that depends on the wording
> of the copyleft license. Some examples:

To pick one of the more extreme-sounding examples:

>     3. Creative Commons ShareAlike: "You may distribute, publicly
>        display, publicly perform, or publicly digitally perform a
>        Derivative Work only under the terms of this License,". "Only",
>        here, seems to preclude dual-licensing to me, too.

"Only" - but for that work.  As I understand dual-licensing, as the author 
distributed their work to you, you (the recipient) get to decide which 
license applies to that action.  Perhaps that "only" applies only to the 
copy you decided to apply the ShareAlike license to.  If you downloaded it 
a second time, say, and said "this second copy was distributed to me under 
the GFDL", then presumably the ShareAlike license doesn't apply to that 
second copy.  Then the question is, can you take the same modifications 
you made to the first copy and apply them to the second?  Since you are 
the copyright owner of the modification, I assume you can - it's the 
combination of the original and your modification that creates the 
modified work that the ShareAlike or GFDL applies to, but not the original 
modification.

Again, IANAL, it would be nice to see where I'm wrong on this.

> So, I think the answer is: kinda.

Seems more definite to me; and it passes the gut-check too, as it also 
seems unlikely that any author publishing under two licenses would intend 
to only allow derivative works under only one license.

 	Brian