Purchase VS/MSDN on a Microsoft Enterprise Agreement
Like all Microsoft products, you can purchase products on a Software + Software Assurance. Software Assurance (SA) is a maintenance that enables you to upgrade the product to the latest version at no additional cost. Visual Studio is sold in this model, however, the SA is the MSDN Subscription with the license as illustrated in the below image. SA (a.k.a MSDN) is a requirement when purchasing on an Enterprise Agreement.
In addition to providing the SA to Visual Studio, MSDN Subscriptions enable your development teams to build robust development/test environments by providing all-you-can-eat access to any Microsoft Enterprise product. Rather than having to separately license each developer with licenses to develop with SQL Server, Win Server, SharePoint, CRM, etc… an MSDN subscription covers them.
If you’re a Government Agency wanting to purchase Visual Studio with/without MSDN on your agencies’ Enterprise Agreement, you do this via the Government Reseller that manages your EA. If you’re not sure who that is, contact your procurement contact or me and you will get pointed in the right direction.
The below graphic illustrates the License + Software Assurance Model for 2008. To understand how this roles into the new 2010 offerings, see here.