IIRC, System.include should reference the case-sensitive name of the actual .js or .pjs filename installed on your system in the libraries folder.

IIRC, This works sort of like sounds or fonts. I believe that System.include also requires that the library be included (checked) for at least one activity in the system such that the file will be downloaded and available in the Control Panel. So, if you have a set of libraries that you need to access using System.include, simply create an unused activity and check (add check mark) for the libraries you'd like to use with System.include.