JMS pitched B5 to Paramount. Paramount declined. Shortly after, DS9 was announced.
People who think DS9 is a ripoff simply because it used a space station setting like B5 need to get over it. Other than being space station based, they have little in common.
So what if Paramount was pitched B5, liked the space station setting, and decided to use it for their next Trek show? No one owns such broad concepts, and it makes B5 fans look petulant to still be on about this almost 20 years later.