Copy the jar to your computer and execute:
$ java -jar <path-to-mjargon.jar> <.mjargon-file>
where path-to-mjargon.jar is where the file was copied and .mjargon-file is a Music Jargon file. See the end of the tutorial for a well known riff.
If you are running on linux you may be able to set an alias for the command to avoid the java -jar part. If running on a bash based system, add the following in your *.bash_aliases:
alias mjargon='java -jar <path-to-mjargon-.jar>'
Then you can execute simply:
$ mjargon <.mjargon-file>