The licence
No account, no server, and no phoning home every time you open the app.
When you buy, you get a piece of text starting with VF1. You paste it into Settings › Licence and VoiceFlow checks the signature on your own Mac, against a key it carries inside. No server is asked anything, not when you activate it and not afterwards.
That means something worth saying plainly: if we disappear one day, your copy keeps working exactly the same.
The licence includes a year of new versions. After that year you lose nothing: VoiceFlow Pro stays yours forever on every version released within that period.
All that happens is that later versions stop being offered. The app doesn't install them precisely so it can't drop you out of Pro by accident: it tells you they exist and you decide whether to renew.
The licence is kept in your iCloud Keychain, so it shows up on its own on your other devices. If you'd rather not depend on that, keep the text: it activates it again whenever you want.
Thirty days, no questions. You write, it's refunded, done: nothing to justify and no form to fill in.
You get the amount back minus the payment processor's fee, around €2. We don't have that part: the bank keeps it at the moment of the charge and it doesn't come back on a refund, so returning it would mean paying out of our own pocket for a sale that never was one.
That said, you probably won't need it: you get 14 days with everything in Pro before paying, and if it doesn't win you over, the free plan doesn't expire. You can find out whether it suits you without risking anything.