The current version of the protocol is 2.02.
Click here to download the latest specification in PDF format: PosiStageNetprotocol_v2.02_2016_09_15.pdf
A sample implementation, provided by VYV, is available and can be used to test your own implementation. It is meant for use with Visual Studio under Windows.
You can download the sample package here:
There is also a separate implementation of PSN for .NET done by David Butler, which you can find at www.theimpersonalstereo.com/posistagedotnet/ .