Religious morality is different from having a moral system. Religious morality is established on stories and events from the past that are used to defend the acts that religion forbid or requires. On the other side, morality is based on the goodness of acts.
It is possible for a person to not believe in God but still have high morals, their understanding of right from wrong is independent to God’s beliefs. The Divine Command Theorists, however, believe God decides what is good, and the opposing side is that the good is already good and God just accepts it as being so. This argument is important because it comes in question whether morality existed before God or vise versa.