There has been a lot of questions regarding licensing for SQL and System Center 2012. As long as you only use System Center Products on a SQL Server then the SQL Server license is included in System Center.
But what about running the Self Service Portal which is a Sharepoint site using the same SQL Server? I asked Microsoft about this and after some time I got the answers below from the licensing group.
Q: If the customers is using the SQL Standard license that is included with SC to run the SharePoint 2010 server that is hosting the SCSM self-service portal, SCOM web parts, etc and the SharePoint server is being used exclusively for SC, does the customer need to pay extra for the SQL license since it is being used to run SharePoint?
A: if the instance of SQL Server is being exclusively used to support SC, then they don’t need an extra license.
Q: If the SharePoint server is not being used exclusively for SC content, does the SQL Server need to be licensed?
A: Yes.
