SimpleIDE Propeller "Run with Terminal" Error

I'm attempting to push test code to my propeller from Ubuntu 16.04 with SimpleIDE 1.0.1 and am getting the following error:

propeller-load -Dreset=dtr -I /opt/parallax/propeller-load/ -b ACTIVITYBOARD cmm/Welcome.elf -r -p /dev/ttyS0Error is : Permission denied
error: opening serial port '/dev/ttyS0'

Error is : Permission denied
error: opening serial port '/dev/ttyS0'

Is this an issue with the FTDI driver, or actual permissions? I've tried a few different things and have not had any success in getting the propeller to work with Linux. Any suggestions are greatly appreciated. Thanks.