There is no fundamental difference between what is called a 'stepper motor' and a 'brushless DC motor'. Either can 'step' or 'run' according to the drive electronics. Both require electronic drive circuits to rotate to a step or to spin.
A CDROM motor with 9 stator windings and a 12 pole rotor (6N + 6S), although designed to spin a CD continously, will behave like a 10 degree stepper motor - energising the coil terminals with DC in the right sequence will result in 36 different rotor positions. Energising the coil terminals with DC quickly in the correct sequence (ie. AC) will result in smooth rotation, just as energising the coils in ANY stepper motor with the correct phase and amplitude will result in smooth rotation.