Dual licensing with two copyleft licenses

[Chad.Woodford at windriver.com]

> -----Original Message-----
> From: Evan Prodromou [mailto:evan at bad.dynu.ca]
> Sent: Friday, December 03, 2004 9:45 AM
> To: Brian Behlendorf
> Cc: Open Source License Discussion List
> Subject: Re: Dual licensing with two copyleft licenses

> I don't think copyright operates that way. I think, in the world of
> copyright, those two copies you downloaded are the same work.

That is true; they are the same work.  But that doesn't mean that that work
cannot be available under two different licenses.
 
> However, most licenses aren't created with dual-licensing in mind (the
> MPL being a noteworthy exception). They're designed to be monolithic,
> and when you mix-and-match them, you don't always get the results you
> expected.

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).  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.  Contributor2 comes along and decides to make modifications.
Contributor2 can take the A-licensed original and the A-licensed
modifications from Contributor1 and make new modifications licensed under
license A.  The same can be said for B.  This continues to work all the way
down the chain until a contributor chooses only a single license for their
modifications.  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?

IANAL.

Chad