That’s the same thing. :) If you reduce computing load, you reduce the need for costly hardware and you reduce the need for energy, thus you reduce the amount of money needed to build and run your setup. There’s a saying in (software) engineering : “reducing energy consumption and increasing performances requires the same optimizations”. Make your code faster (by itself, not by buffing up hardware) and it consumes less energy. Make your application simpler, and it will run faster, and it will consume less energy. It’s not an absolute truth (it sometimes happen that you make your code faster and it consumes more energy), but it’s true most of the time.
This. Nothing is more difficult than understanding someone’s else code and architecture, and even if you manage that, you’re now stucked with the choices somebody else made and nobody wants that (we want to make our terrible choices!).
More than a final app, the best thing to publish as FOSS is libraries extracted from it to help other developers build there own products faster. That’s something other may want to maintain when we abandon it. And on top of that, it still help to publish your app using this lib to serve as practical example about how to use your it, of course.