The iPhone 4S on Sprint appears to be unlocked, at least that’s the conclusion we draw from a leaked carrier memo that also states that iPhone 4S devices will be SIM-locked upon activation starting today.

Starting today “all iPhone 4S devices will have the SIM locked”. The procedure will be done at activation and will be invisible to the user, also without the need of Sprint personnel intervention. This is what awaits you starting today but if you got an iPhone 4S from Sprint prior to November 11, this will not affect you at all.

Source: Sprintfeed