SQL Server Reporting Server Migration
You already are not using the &quot;same license&quot; for both servers. SSRS is part of the SQL Server license (Standard Edition and above), but it's only covered by your SQL Server license on the same server. IOW, if your report server is on Server A and SQL Server is on Server B, you need to license them both.
So yes, if you have acquired a license for Server B to upgrade SQL Server, you can do that without touching Server A (report server). Server A will continue to be covered by its previous license.
Verify with whomever handles your SQL Server license purchases.