Hongli, Ninh, I've always loved Passenger (it's running almost all of my Rails apps) and am happy to see you guys try to get paid directly for all the effort that went into Passenger.
I just wanted to add my voice that I think it'll be useful for developers to know what you guys intend to do with the open source version now that you've the Enterprise version. A comparison table like mlitwiniuk mentioned would be useful.
Would also like to know when the open source version of Passenger 4.0 will be available so I can decide whether to pay for a few Enterprise licenses now or hold on.