'spot' and ''OTFProof.py' use the same C library, but are different programs. 'spot' is a stand-alone command-line tool for Mac and Windows. "OTFProof.py" is a Python script that providesa a graphical user interface, but which requires that you have Python installed on your system, and that you have completed the FDK install inall its details. Both provide exactly the same reports. You will find spot one directory level down from OTFProof.py. in the sub-directory named osx or nt.