I see that you wanted to know of any license violation which using BYOL for Oracle on RDS.
I would suggest you to check with Oracle for this query as they would issue you the license.
From AWS standpoint - please check the link below. Except from the link "To run a DB Instance under the BYOL model, you must have the appropriate Oracle Database license (with Software Update License & Support) for the DB Instance class and Oracle Database edition you wish to run. You must also follow Oracle's policies for licensing Oracle Database software in the cloud computing environment. DB Instances reside in the Amazon EC2 environment, and Oracle's licensing policy for Amazon EC2 is located https://www.oracle.com/us/corporate/pricing/cloud-licensing-070579.pdf"
 Oracle licensing options - Bring Your Own License (BYOL) - https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Oracle.Concepts.Licensing.html#Oracle.Concepts.Licensing.BYOL
Again, RDS is a hosting platform in this scenario not the license issuer. I sincerely hope I was able to shed some light on the matter for you from AWS standpoint. Have a great rest of the day!
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