Don't know about this myself, certainly won't need to use it, but on the Alien RPG group I see people are a bit confused about the necessity of this this app. This is not an official FL product as far as I'm aware. Especially cause you need to buy everything there again, unlike the modules in Foundry and Roll20 where you get everything if you own the books. And you already have fan sites that have generators for planets and events... From my understanding, the nexus doesn't offer anything particularly new or useful.
Whatever the case may be, glad there's buzz about the RPG.