I predict one of the two following things will happen:
1) Once OpenCoin releases the source for the Ripple server, we will find a way to fork the project and create a version that does not require XRP to function.
2) OpenCoin will never open source the server, making their claim of decentralization a lie.
consider that, not only is OpenCoin really closed ClosedCoin for all intents and purposes, but they have also given no indicator as to what open source license they plan to release the code under. Secondly you also have the issue of patents, which rules out the possibility of forking the way you describe.