Microsoft Windows Rights Management Server 2012 can augment an organization's security strategy by protecting information through persistent usage policies, which remain with the information, no matter where it is moved. You can use AD RMS to help prevent sensitive information—such as financial reports, product specifications, customer data, and confidential e-mail messages—from intentionally or accidentally getting into the wrong hands.
Microsoft Licensing: An External Connector grants access to the server by an unlimited number of external users such as business partners, suppliers, customers, retirees, and alumni. Basically, an external user is a person who is not an employee or similar personnel of the company, such as a business partner or customer. With this license you do not need to buy individual CALs. It is licensed per server. This license comes with Microsoft's maintenance plan, Software Assurance.