Well it does actually have a small dependency, Robot Building for beginners does actually use DC motors, but they didnt have a MCU, if you put together a gearbox out of lego gears and couple your DC motor to it, it could work, but if you have an MCU it is much easier to control a servo, motors are simply on/off they arent picky, where as servos require a pulse between 1 and 2 ms.