Licensing SQL Server 2005 on virtual machines

I check the licensing of SQL server 2005 for one of our clients which going to consolidate 5 SQL server to one virtual machine running 5 different instances as part of a big DRP project that we design for him.

Licensing SQL server on a virtual machine

According to Microsoft, there is three different approaches:

1. For Standard, Workgroup, and Enterprise, if you decide to license on a per processor basis, you must buy a SQL Server license for each virtual processor.
2. For Enterprise Edition, you can also choose to license all physical processors in a box. This gives you rights to run SQL Server on unlimited number of virtual processors running on the same machine.
3. For Server/CAL mode, for Standard and Workgroup, you must obtain SQL Server licenses for each Virtual Operating System Environment on which you run instances of SQL Server. However, for Enterprise, if you have a Server license for the physical Server, you may run unlimited instances of SQL Server in any Virtual Operating System Environment that you run on that same machine.

For more detailed information please read: Microsoft Virtual Server Licensing Document

Licensing SQL server 2005 Instances

According to Microsoft You can run multiple instances of SQL Server 2005 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 2005, you can now run multiple instances with the Workgroup, Standard, and Enterprise editions when they are licensed server/CAL or on a per-processor basis. (taken from: http://www.microsoft.com/sql/howtobuy/faq.mspx)

Were going to use this knowledge for optimizing the license for this customer and save him money along with giving him a more redundant environment.