All i have to say is Liberty Reserve...same fate for Ripple.
Completely different situation.
Opencoin operates in the US under US law.
Opencoin is in the US and under US law, thus it will be even easier for the US to shut them down than it was for LR. Look at how easy it is to open an anonymous ripple account: they don't even ask you for a name and email address.
As OpenCoin has stated, even if that would happen today before the source code was released, they would just at that moment, release it. Wouldn't matter what happens to OpenCoin after that, as it relates to the Ripple network.