With Amazon RDS, you can provision and scale a relational database (and the underlying infrastructure hardware and software) in just minutes using the point-and-click interface of the AWS Management Console. Amazon RDS also manages time-consuming database administration tasks, including continuous backups, software patching, and exposing key operational metrics. Running Oracle Databases on Amazon RDS enables you to extend the ease of use and management capabilities of Amazon RDS to the Oracle Database Software.

AWS plans to offer a variety of licensing options for running the Oracle Database on Amazon RDS, including:

• “Bring Your Own License” – (BYOL): Customers with existing Oracle Database licenses can apply them to run Oracle Databases on Amazon RDS with no additional software licensing or support charges.
• On-Demand Database Instances (DB Instances): This pay-by-the-hour licensing option requires no pre-existing licenses, up-front fees, or long-term commitments to run Oracle Databases on Amazon RDS. Customers pay a simple, hourly rate per RDS Database Instance running Oracle Database 11g. The hourly rate depends upon the Oracle Database edition and DB Instance size option selected.
• Reserved DB Instances: Reserved DB Instances allow customers to make a low, one-time payment for each DB Instance and in turn receive the option to run that DB Instance at a significant discount on the ongoing hourly usage charge. Both one-year and three-year reservation terms will be available.

Source: Amazon Website Update