It would be because cron runs as the root user.

Castget probably looks at the file path $HOME/.castgetrc. For your regular user, $HOME is probably /home/myamazingusername. For the root user, $HOME is probably /root .

You can get a root terminal session by running sudo -i in a terminal console window. You can try running castget there to see what happens.

Sudo -n:

-n, --non-interactive
  Avoid prompting the user for input of any kind.  If a
  password is required for the command to run, sudo, will
  display an error message and exit.

It’s just a nice thing to put in non-interactive scripts that use sudo. Sometimes you can end up with scripts that just wait endlessly for a password that will never be input because the script is being run non-interactively. The flag probably isn’t needed for a cron job, because root probably can sudo as any user without a password, but it doesn’t hurt either.

EDIT: I didn’t know that there are user crontab entries as well. If you just used crontab -e without using sudo, then you don’t need to worry about the job being run as root.