Is it possible to find how this is done and cheat? Sure.
Premium status is checked and updated when online, and the state is cached until the next time.
We’ll enable pure offline registration in the not too far distant future, if nothing else to ensure everyone that regardless of our servers or our business still operating you can always access your files, even after getting a new computer. Currently you do need server access the first time you install AxCrypt on a new computer, but not thereafter. But plain encryption/decryption is of course fully offline functions. AxCrypt works fine in offline mode with no Internet or server access, except of course for the features which are server based.