Andy Leonard (12/17/2007)
...* My understanding of this: Microsoft allows you to install as many instances of SQL Server on a single box as you desire. For example: If you purchase a 4-chip license for SQL Server 2005 (or 2008 - I believe they're the same price) Enterprise and the server is built with four quad-core processors, you can install a couple larger instances and set processor affinity to utilize 4 cores each, then install a couple more smaller instances utilizing a couple cores each - all for no additional charge.
It depends on the version of SQL Server. Technically (I studied this earlier this year) if you're running SS 2000 Standard Edition, if I recall correctly you have to have a license for each named instance. If you're running Enterprise 2000, you can have an unlimited number of instances on the same server with no change in licensing.
I also looked at the licensing requirements for 2K5 but I don't recall them off-hand.
I believe that you also get licenses for development through certain MS subscriptions, but I have no specifics on that.
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