It's neither of those, but a yearly subscription for updates - maintenance period. If you don't renew the license, the already licensed versions won't expire.
Here's described how it works: https://www.hwinfo.com/licenses/
Is it possible to deactivate one of the five PC's if you need to reinstall? I reinstall quite often and would like to use the Shared memory feature... I don't believe it would be worth it if I can't pull back one of my five uses if I need to reinstall.