In this particular case, the Light charity is like a bacteria that you've engineered to produce a desired protein that you want that is not needed for its own survival. When you put these bacteria in a bioreactor, mutations inevitably take some back to the wild type, which don't make that protein but put all their energy into reproduction. They quickly take over the bioreactor and drive the "altruistic" bacteria into extinction. This is not a PD case where some equilibrium arises between exploitation and cooperation. Without some countervailing force not specified here, exploitation wins.