One person makes this app, and reads every message.
Email kjoysky31@gmail.com with any question or problem, and I will get back to you.
You can also write from inside the app — open Settings (the cog at the top of the screen), then Write to the developer. A message sent that way includes your app version and iPhone model, so a problem can be found faster. No readings are ever sent.
Everything you record stays on your iPhone and in your own private iCloud. Nobody else can see it, and nothing is collected about you. The Privacy Policy has the whole picture.
Pro is billed through your Apple account, so it is managed or cancelled in your Apple account settings, not in the app. The Terms of Use describe what Pro adds.