A basic understanding of SQL Server licensing is essential, especially when changes are afoot, as they are with the upcoming release of SQL Server 2012. The big news for SQL Server 2012 licensing is the change from per-socket to per-core licenses for the Enterprise edition. The easiest way to explain the difference is with an example.
Let's look at three systems: Server1 with two dual-core processors, Server2 with four quad-core processors, and Server3 with four eight-core processors. As Table 1 shows, if all three systems are running SQL Server 2008 R2 Enterprise, you'd have two, four, and four licenses, respectively. In SQL Server 2012 Enterprise, you have to license per core, with a minimum of four cores per processor socket. So, if you want to run the Enterprise edition on all three systems, you have to buy 8 core licenses for Server1 (because you have to buy the minimum number of cores), 16 core licenses for Server2, and 32 core licenses for Server3. The current published list price for a core license for SQL Server 2012 Enterprise is $6,874 per core. In comparison, the current per-socket license for SQL Server 2008 R2 Enterprise is $27,495. As you can see in Table 1, there's little change in the licensing costs for Server1 and Server2, but the cost for Server3 doubles with the new licensing structure.
Note that there's a "core factor" for AMD processors of .75, so AMD cores will require fewer core licenses than Intel processors. In other words, for Server2, you'd take the number of cores (16), multiply by the core factor (.75), and thus be required to buy 16 * .75 = 12 core licenses if Server2 were running AMD processors.
Licensing for the Other Editions
Core licensing is available for SQL Server 2012 Standard, but you can still use the Server + CAL license model for this edition. (You can't use the Server + CAL license model for the Enterprise edition.) Standard edition core licenses are $1,793 per core or $898 per server in the Server + CAL model. Whether it's better to use the per-core licensing or the Server + CAL model for your Standard edition system depends completely on the implementation. You'll likely need to work with a Microsoft or Microsoft partner licensing specialist to figure out how to get the lowest price.
There's a new SKU for the new Business Intelligence edition of SQL Server 2012. This SKU will only be available with the Server + CAL model. The SKU is $8,592 per server, plus CALs.
If you're using CAL licensing, the CAL must be at the highest version of SQL Server that you're using from the device. In other words, you need a SQL Server 2012 CAL to talk to a SQL Server 2012 Standard or Business Intelligence system. You can't use a SQL Server 2008 CAL, for example.
The list price for a CAL is $209. A CAL is required for each user that connects to a SQL Server system. However, one CAL is good for any number of SQL Server systems, as long as you're connecting to an equivalent or lower SKU. For example, if you buy a Business Intelligence edition CAL, you can connect to Business Intelligence edition systems, Standard edition systems, or systems running an earlier version of SQL Server (e.g., SQL Server 2008 R2, SQL Server 2008, SQL Server 2005).
Note that there is no longer a Datacenter edition SKU because the Datacenter edition has been rolled into the Enterprise edition. Also note that the Small Business edition (available only to OEMs) and Workgroup edition are being retired. There is no change in the licensing for the Developer edition of SQL Server 2012
Licensing SQL Server 2012 VMs
Virtualization is explicitly addressed in the licensing structure for SQL Server 2012. You can either license individual SQL Server virtual machines (VMs), or you can license the Enterprise edition on the host for all cores and run as many VMs as you would like. If you choose to license individual VMs, you must purchase either a minimum of four core licenses per VM or purchase a server license plus CALs if you're using the Standard or Business Intelligence edition.
Upgrading Existing Licenses
In terms of upgrading existing licenses, there are a number of provisions and caveats. You'll probably want to consult a Microsoft or Microsoft partner licensing specialist to fully understand the considerations for moving your existing licenses to SQL Server 2012. Having a Software Assurance (SA) agreement or an Enterprise Agreement will affect your options.
See also, "Microsoft SQL Server 2012's Editions and Licensing."