[a_c_s]

There is an unlock for the phone itself, which you appear to understand, which allows you to flash custom ROMs...then there is a separate unlock for the security side, which allows you to flash a new radio, and also unlock the GSM card...as somebody eloquently stated earlier, this theoretically would allow you to use any GSM carrier once unlocked, though you'd still need to pay for the service...but you cannot use the same process to move between CDMA carriers...