Hi Ellen,
Unfortunately I do not have a mac to test or provide any other advice. I would think that mac should work the same way as a Linux OS, as they are essentially the same thing. One thing you need to make sure is that the file has the proper ownership and it has the executable flag. In a console, you should go to the directory containing the executable file and type ls -la and it should tell you if you have the x attribute set for the current user (as a minimum). If this is not clear, please paste the line related to your executable file produced when you execute the ls -la command.
Not sure why that wouldn’t work. Maybe because you are running in headless mode? Add a println in setup and see if you get data in the console when you execute the program.
Related to other contributed libraries, I can only suggest to copy the jar of those libraries in the folder named code which should be created by you (if you don’t have it) and it should be place within your sketch folder, at the same level as the data folder. However, I am not 100% sure you need to do this as I’ think processing-java should be able to find those libraries, if you are calling this function within the sketch folder when building your code. However, I do not use this command line feature of Processing that often… so I am not sure about the mechanics under the hood.
Kf