Blue Coat has created 1 Technical Add On for getting the data into Splunk and 1 App for dashboards around that data for the latest ProxySG. The TA is using the custom client to receive the data at this time. Ive included the documentation here that is available as well on BlueTouch Online in TAP Integrations.
Anyone is free to create apps based on any Blue Coat products, but Blue Coat only supports the ones created by them.
Also just so you are aware, the 3 other Blue Coat apps you created tags for are for 3 other Blue Coat products. There is ProxySG as you are aware but there is also an App for Security Analytics and an App for Malware Analysis.