Purchase VS/MSDN via GSA
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.
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 GSA, you do this via one of our Government Resellers. Not that your Agency may have a Microsoft Enterprise Agreement in place that might provide better pricing/terms. Only the Reseller who manages your Enterprise Agreement can sell you licenses on it so talk to your procurement contact to understand your options.