No product keys to lose, no accounts to create. You activate with the same email address you paid with — that's the whole system.
Every product ships with a launcher that installs and updates it. Grab it from the downloads page or from the link in your purchase email.
Run the launcher and type the email address you used at checkout. It confirms the purchase with the server once, and the full version unlocks.
No sign-ins and no product keys. The app shows who it's registered to, and the launcher keeps it up to date and quietly re-confirms your purchase every few months.
Yes — your licence covers the computers you personally use. Run the launcher on each one and enter the same purchase email. There's no device limit to track and nothing to deactivate when you replace a machine.
Only your purchase email — when you activate, and again every few months to re-confirm the purchase. The server answers whether that email bought the product and the name given at checkout, which the app shows as "Registered to …". Nothing about your computer is collected, and the app itself never contacts the server while you use it.