I know everyone's feelings regarding spec work & crowd sourcing but what if it was all for charity?

I came across this site - The Big Picture | Corbis Design for a Cause Contest - and you have to design a poster in support for a charity of your choice using one or more images provided by Corbis.

The outcome if you win, is the charity you designed for gets a 1000 donation...

However, corbis obviously get their images out there and the designer gets their work featured in various magazines / exposure blah blah blah.

Is this just Spec work / crowdsourcing or is it a bit more morally acceptable to designers?

Thoughts?...