Licensing. Sometimes it feels like to you need a specialized degree, a black robe and a secret handshake to really understand it – but it’s not quite that bad.
There are several licensing “models”, from just buying SQL Server off the shelf to Software Assurance, or SA, where you just install to your heart’s content and then “true up” or pay at the end of a certain period.
But it’s best to go to the source. There are three guides I use:
This is the more complicated but more complete guide: http://download.microsoft.com/download/6/F/8/6F84A9FE-1E5C-44CC-87BB-C236BFCBA4DF/SQLServer2008_LicensingGuide.pdf
And this is the phone number I call when I’m stumped: (800) 426-9400
They key is to pay for what you use. All of us have had Instance “pop up” in the organization without our knowledge. If that happens, contact that number and ask what to do. Nobody will come to your organization and take you to court – in fact, you’ll find that we’ll work with you to help you stay current. We’re all headed the same direction – trying to make sure SQL Server solves business problems in your company.