Luckily it’s DRM-free. Back up your installers. I wanted to call attention to this, because in a very unusual move, it’s being removed even for people who own a copy, whereas usually stores will only remove a game from sale and still host the files for existing owners to download.
No announcement or confirmation from Night School Studio regarding GOG, Steam, the Playstation Store, or the Nintendo eShop as of yet. My guess is they would give a decent warning announcement if it were to leave those outlets as well, but regardless I did download my copy from GOG to my backup drive just in case.