One day in the future, there will be more "dead" software than "alive".

All software is kept "alive" by human effort. As hardware, operating systems, drivers, and runtimes change, all software is kept running by additional human intervention. Even physical media like DVDs and cartridges will degrade at varying speeds. Bits containing an unlocked installer must be stored somewhere. Consoles stop working and need components replaced.

Software is the music that we play, it just takes a few decades for the echo to stop reverberating.

Websites are the worst. How many versions of gmail.com have been discarded for us to get to the current version? I'm sure Google currently has them backed up, which will survive until Google goes away and the millions of versions will likely disappear like vapor in the sun.

Software with a required public API will likely end soonest. If it needs an old architecture or hardware, that is a risk. If you have an unlocked installer, what OS dependencies does it have?

Someone in this chain said they only feel like they own software if they have the source code. Which is another way of saying, if they have the sheet music, they can play the song themselves. But it isn't "permanent" it's just another song in the wind.