Thomas,
I'm with the others in that if they truly just wanted to use features, they would simply use the code (under GPL). RoundCube is a real threat to them, in my opinion - and theirs, I am sure. I've never really been a fan of the commercial-with-crippled-open-source-variant model, either.
I'd take them up on the consulting work if they still would offer, though :)
Adam