Dual licensing with two copyleft licenses

[Brian Behlendorf]

On Thu, 2 Dec 2004, Evan Prodromou wrote:
> 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.

Can't Bob make that decision twice?  Release two packages, one under 
license A, one under license B, both of them the same package of the 
original work plus his modifications and thus, the same work?

If Bob can do that, what keeps him from optimizing by having one package 
with a choose-one-of-two license, like Alice did?  So long as following 
the terms of one of the license didn't require a particular modification 
that the other license disallowed, I suppose.

 	Brian