[RIMR]

If paying for something deanonymizes me, as a Google Play purchase would, then it isn't fulfilling the privacy part of the deal at all.

More importantly, if privacy centric apps raise the barrier for entry to include licensing fees, then most people are going to choose the "free" alternatives that get paid for by selling their metadata. If you actually care about protecting users' privacy, you should avoid gatekeeping the technology behind a paywall.

There are plenty of Free (as in beer + as in freedom) period trackers out there that I would be happy to donate time and money to help develop. The closed-source for-profit version that demands that I disclose my identity to Google before I get started is dead-in-the water, having failed to be suitable for any purpose than making the developer a bit of cash while pretending to care about women's privacy in a world that wants to imprison them for a miscarriage.