Add a shiny gold sticker to your title screen reading "Registered Shareware!"

That's it. That's all this DLC does. It adds no further functionality than a shiny gold sticker.

Because The Shadow Over Cyberspace is a fully-released, fully-free game with no free-to-play elements and no microtransactions, the "Shareware" donation is a way of saying thank you to the developers and compensating them for their hard work.

It's entirely optional. Appreciated, but optional. Have fun facing digital cosmic horrors, either way!