I think it's both - yes, revenue is a component of this (as far as sources go), but I really do think that we can get to pretty complete transparency without making source openly available. For instance, bringing customers in on things like specs, bug tracking, enhancement requests, etc. is a great start. Having wider community tech previews should help as well.
FWIW, I'm also interested in seeing how this goes - I've subscribed to the threads about the videos that I've done - so I'll be keeping up (love that RSS)