Windows Server Update Services (WSUS) Licensing
As mentioned during our Momentum events, if you are running Windows Serve 2003 you are already licensed to run WSUS. Windows Server Update Services 3.0 is free and is available to download at no cost. Each managed client requires a Windows Server CAL.
WSUS can use MSDE, WMSDE, or SQL Server. If you choose to use SQL Server as its datastore, then SQL Server needs to be licensed appropriately, with either a SQL Server CAL for every device managed by WSUS, or a per-processor license.