Shouldn't apps be runnable forever as a way to remember dead authors?

Should? How would that work? All hardware, OS, library, and platform vendors either stop making breaking updates, or provide sandboxes to run old apps? Since most apps just front-end some SAAS in the cloud, who will keep that running?

If you want your code to live forever, or as long as anyone finds it useful, make it open source.

The dead don't care if anyone uses their apps, not sure what good it does to "remember dead [app] authors." Should I continue to accumulate junk in the garage to remember my dead father, or take up sewing to remember my grandmother?