As I don't have access to earlier versions of BizTalk, the sample application is compiled for BizTalk 2013 R2 (.Net 4.5). Nothing has changed so you should be able to download the source and compile it for earlier versions.
for more information: blogical.se/blogs/mikael/archive/2012/05/28/rest-start-kit-for-biztalk-server.aspx
Some minor changes has been made since the 1.0 package:
- Remove namespaces from json
- Manually copied headers from incoming message to support Azure Service Bus
- Fixed outgoing Content-Type to be application/json when Accept is set to appplication/json