VistA Viewer is a VistA developer tool that helps exploring various VistA components in a web-browser. It is an application written using EWD 3 (http://ec2.mgateway.com/ewd/ws/index.html). User can review VistA patches(builds) and VistA Kernel components - Remote Procedure Calls (RPC), Data Dictionaries, Rouitnes, Options, Security Keys, Parameters, etc. User can test VistA RPC.
For installation instruction and description refer to http://nikolaytopalov.wordpress.com/2014/05/15/vista-viewer