Upgrade your license to an Ultimate license and you can let anyone join your game with only the Demo here on Steam or on the FG site. Your new license key will replace your old key.
http://store.steampowered.com/app/300870/?snr=1_7_7_151_150_1
For D&D players and DM's, you can pick up a copy of the Sword Coast Adventurer's Guide with detailed information about the area surrounding most of the adventure paths and new player options.
http://store.steampowered.com/app/415570/?snr=1_7_7_151_150_1