The app itself
No account, no sign-in, no licence check, no telemetry, no usage statistics, no crash reports. Purify does not ask who you are and has nowhere to send an answer.
The only network request it ever makes is the update check, and only when you press the button: it asks this site for a small file and compares version numbers. That request reaches our host the way any web request does, and it carries nothing about you or your PC.