How does licensing work with the multi-instance feature in SQL Server 2008?
A. You can run multiple instances of SQL Server 2008 on a single computer. Multiple instances are used by organizations that have several applications running on a server but want them to run in isolation so that any problem in one instance will not affect the other instances. In SQL Server 2008, you can run multiple instances with the Workgroup, Standard, and Enterprise editions when they are licensed server/CAL or on a per-processor basis. Please read the SQL Server 2008 Licensing Overview for more information.