The ISAAC pipeline is entirely based on the eclipse library. You need to download the library to compile the pipeline. Both packages can be found at:
Installation instructions are provided with the package and on the Web site. After installation is complete, you should end up with a number of executables in eclipse/bin. The main program you are looking for is called isaacp, it contains the recipes for most of the ISAAC data reduction modes, together with some basic documentation for the command usage.