1) He'd have to license it under the BSD and GPL from the get-go.
2) Licensing it BSD like that- why bother with the GPL in the first place?
Licensing isn't something you can really honestly play games with. It's the rules by which a rights holder gives out rights to use a piece of software, make publication copies or derivative works, and so forth. If you don't do it right, you can inadvertently place the code into a realm of unsuitability for use like I've alluded to in other posts.
The GPL (even V3, but it's a bit more verbose than I think it needed to be- but they felt that they had to boilerplate it up a bit because of people trying to find and mis-use 'loopholes' in the prior versions of the license...) is a brilliant idea and if used right (see Linux...) it can do amazing things for everyone involved. But you need to understand what you're doing when you place things under that license- or any other license for that matter.