Perhaps I should amend my statement: "such that they would fall apart as soon as we stop putting energy into maintaining hardware and software dependencies" So

Perhaps I should amend my statement: "such that they would fall apart as soon as we stop putting energy into maintaining hardware and software dependencies" Software assumes that there exists specific hardware, operating systems, and services underlying it to keep operating. If you try to turn on a 5-year old android phone, you will find that your apps probably don't work (because of service changes for example), but also can't be upgraded because the latest versions don't work with your old version of android, and your android can't be upgraded because the latest versions don't have device drivers for your phone hardware. You're SOL. So, to have a 100-year software, you need commodity components from the top down, that continue to be maintained for the same length of time. And it all probably needs to be 100% open source. Otherwise, you have perishable software.