This repository contains the source code (plus some "bit rot") of the SHIFT compiler and runtime. Most of the code is from a 1998 download, which should include the latest embodyment of the tool.
The original README has instructions about how to build and run the system. You should be able to build and run the compiler and the generated code with GCC on Linux/MacOS (or Solaris) without much pain. Using the Tcl graphical interface will require much more work.
Feel free to contact me if you want to do something with the code. I can try to help you.