Windows Azure AppFabric SDK V1.5 - September 2011 released during the BUILD is now available for free download through Microsoft Download Center.
"Windows Azure AppFabric is a key component of the Windows Azure Platform. It includes three services: AppFabric Access Control, AppFabric Service Bus and AppFabric Caching Service."
"This SDK includes API libraries for building connected applications using Windows Azure AppFabric."
"It spans the entire spectrum of today's Internet applications - from rich connected applications with advanced connectivity requirements to Web-style applications that use simple protocols such as HTTP. This enables services to communicate with the broadest possible range of clients," stated Microsoft.
This page also includes samples that you can download.
The version 1.5 SDK includes an updated Service Bus assembly that includes support for durable, or "brokered" messaging features, such as queues, topics, and subscriptions. These features require the .NET Framework version 4.0.
If you have a dependency on the .NET Framework version 3.5, you should download or continue to use version 1.0 of the AppFabric SDK. However, the v1.0 SDK does not support the new messaging features.
You can download Windows Azure AppFabric SDK V1.5 - September 2011 here.