Dolphin is required to be registered with one license only - it doesn't need/request any additional licenses. Additionally, a license can be used for one domain name only. Dolphin doesn't support subdomain registration.
IE: if you have a license registered on yoursite.com, you cannot register the same license for your.yoursite.com
Still, the same license can be used to register another copy of Dolphin installed on a subfolder - yoursite.com/yoursite