That seems pretty reasonable! It's also AGPL licensed and the source code is available on GitHub. 20 minutes with an LLM would likely yield you a nagware-free version if you value your time at less than $21/hour. Otherwise it costs just $7 to pay Adrian for their good work!

Why, when I could use an AI to both detect the corners and write+run a completely free ad-hoc script to fix the perspective.