There are two executables in the Piscis download:
Piscis Setup - Rapture LE.exe
Piscis Setup - Rapture.exe
I have the full version, so I ran the second one, and it said:
"The Setup did not find Cakewalk Rapture installation in your system. (Re)Install Rapture and run the setup again. This is absurd, since Rapture is installed, registered and available in SONAR X2. I've seen this error before in the distant past, but didn't make a note to myself of how to get around it.