Do I have to sign in?

Once, and it is one trip to your browser. Choose I'm new, give a name and an email address, say whether it is for personal use or for work, and follow the link we email you. You are signed in, offered an optional password, and handed back to the app, which carries on by itself. That is how we know who uses it, and it is the whole of what registration does. After that it works offline indefinitely.

Once is literal. Having verified once, that installation is never asked again, whatever goes wrong afterwards — a lapsed lease, a revoked sign-in, signing out of every account, our service being down for a week. All of those reduce capacity, and none of them puts the sign-in screen back. A machine with no route to the internet skips the sign-in entirely and uses a signed license file instead, below.