Licensing: It's a black art really. If those sisters from Charmed ever came up against an enterprise licensing agreement, I know who my money would be on.
However, I was reading recently that Microsoft are updating their Software Assurance licensing agreement. A number of changes are coming into affect from March 2006.
A few things in particular caught my eye. One is the Home Use policy. This allows employees to install copies of MS Office desktop products at home. Imagine - access to the latest and greatest Office 11 and 12 features from your home PC. It will be like Christmas all over again!
The other interesting amendment is the cold backup licensing. This means that you no longer have to pay for a separate license for a disaster recovery server. The gotcha is that the server must be turned off - i.e. "cold" - until the disaster occurs. You can power it up occasionally to confirm that it is all working, and to perform updates to the environment, but it can't be "warm" - i.e. ready to go in a matter of seconds after the disaster. It also can't be used for load balancing - that would be "hot".
I believe SQL Server supports the cold backup licensing today without requiring Software Assurance. Here's an extract from the Microsoft SQL licensing FAQ:
"Failover support, where servers are clustered together and set to pick up processing duties if one computer should fail, is now available in Workgroup, Standard, and Enterprise editions of SQL Server 2005. Under each of these editions, keeping a passive server for failover purposes does not require a license as long as the passive server has the same or fewer processors than the active server (under the per processor scenario)."
So there you have it - rush out and purchase Software Assurance. As always, consult a trained licensing professional before signing any enterprise agreement. If problems persist, head off to bed and watch Charmed.