Luciferin isn't what makes jellyfish glow, that's GFP. GFP, at least, requires a specific light input to cause the glow (UV at a particular wavelength depending on the molecule). I don't know about Luciferin, though.
Luciferin is what makes fireflys glow. Luciferin really produces light from chemical energy. GFP (Green Fluorescent Protein) is just fluorescent, not luminescent.
luciferin makes the jellyfish glow, by creating the photon that gets transferred to (and illuminates) the GFP.
Luciferin is converted to a reactive intermediate by the enzyme luciferase in a reaction that uses ATP (produced by mitochondria), this intermediate reacts with O2 to produce light.