Are people with dissociative identity disorders psychopaths?

Quite different. People with dissociative identity disorders have likely suffered severe interpersonal traumas. Psychopaths--people with little or no conscience--cause trauma in others.
Not at all. The term "psychopath" usually refers to antisocial personality disorder -- which is a pervasive pattern of disregard for, and violation of, the rights of others. In this there's deceitfulness, consistent irresponsibility, & much impulsivity. Did involves genuine inability to recall important info (more than simple forgetfulness), and multiple distinct identities taking control of behavior.