Does MSSQL RDS Read replica requires separate license?

Hi,

The main question is: What kind of licensing mode do you use? Most customers can only use the license included option as the licensing terms for MSSQL server prohibit the bring-your-own-license (BYOL) mode for most scenarios.

If you use License included then AWS will take care about all licensing for you, as this is part of the service: https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/SQLServer.Concepts.General.Licensing.html

But yes, the read replica requires a license, but it will be included in the service cost.