It looks like in the files the VFXController class is defined as VFXFireController but referenced to as just VFXController so there are parse errors without modifications
I just downloaded it and I had to replace extends VFXController by extends VFXFireController in all three scripts (fire_area, fire_ball and fire_forcefield), as well as add @tool in fire_ball.
I'm only using the forcefield at the moment, and it works pretty well once this was corrected.
