Since the article is about open-sourcing the interface and not the software itself, why only when the product goes end of life?

Also, "end of life" is hard to define. Does it mean not being produced, ordered or sold? After how many days, months, etc.?

I guess it depends? -Software updates no longer available -Customer support no longer exists -End of legal (or voluntary) obligations to stock replacement parts and offer repair services for the hardware