cmdbet is basically a clone of the names we all know. with lower limits and with a nasty tendency to void here and there without a just cause. not all the time, but there have been complaints.
i don't believe the brokerages offer whatever they can get their hand on, if that was the case they would be offering more books and there would be more people getting screwed (which afaik hasn't happened yet with any of the reputable names). that doesn't mean i'd recommend playing with cmd btw, it's all risk vs reward ofcourse