As soon as the server source code is open, it will be very difficult to make changes in Ripple's behavior. Had we released the source code to the public at the same time we made access available to the public, as Bitcoin did, there would have been no chance for public participation in the early design.
Bitcoin was presented to the community as a done deal, take it or leave it. If people had reasons to disagree with the block reward schedule, for example, they had no chance to discuss it or make their case. That was set in stone by the early developers.
We can still make those kinds of changes in Ripple. And we are still discussing structural changes based on community input that will make the system better. See, for example:
https://github.com/rippleFoundation/ripple-client/issues/748
Here's a case where members of the community disagreed with a part of Ripple's design and because Opencoin still runs the majority of validators, it can still be improved. Had we followed Bitcoin's model, we likely would have been stuck with it.
Fortunately, I don't think there's anything in Bitcoin that's bad that we're stuck with. I'm not sure if that's due to luck or just the designer's genius. But we didn't have that kind of confidence, and it turns out that it was probably a good thing that we didn't. There are at least three major things that we're working to improve based on community feedback.