Connecting Non Steam players to Your Project Zomboid server

Login to Command Center.
From the server list, select the server for which you would like to change settings by pressing it's Manage button.
Stop the server.
Click the Files tab.
Click on the file that says ProjectZomboid64.json to edit.
Fine the line -Dzomboid.steam=1 and change the 1 to a 0.
Restart your server and your Non-Steam friends should be able to join your server.