[Someone]

SaaS = “Software as a Service”, not “Software as a Subscription”.

I think it’s when the developer keeps providing a service.

Think of

  - being given a vacuum cleaner
  - buying a vacuum cleaner
  - renting a leasing a vacuum cleaner
  - paying someone to periodically vacuum your house

Only the last, for me, is “as a service”. An app that runs 100% on your system that doesn’t require the app developer to do something specially for you, for me falls under one of the other three (freeware, buying, subscription)

But yes, I agree the OP doesn’t seem to be doing SaaS, either, given that they say the one-time payment covers all expenses (that cannot be true if they are having costs after the sale and that payment is for all time)