Even though it was a joke, expecting to be paid for updating a modification you've made on your own volition is pretty sad, just ditch the modification if you don't wish to update it any further or hand over the development to anyone who's capable and willing to take over for you.
How is that sad? They spent countless hours on making the sprites from near scratch and even more to make the advanced unique coding that goes into making the mod work. So while yes they where joking, it would not be "sad" to not want spend countless more hours trying to update the mod just like that, with starsectors newest version comes alot of under the hood changes that break mods like this 100 different ways, hence why more advanced mods like this and blackrock are not so easy and simple to update.
Besides if they truely dont want to work on it then they are under no obligation to hand over the mod they made to someone else to update, if they wish it to die, then like the valkyre mod, it will stay dead