A native Diarium licensing system would not be a small change. For the App Store and Google Play versions, app store rules also restrict external payment/license flows for digital features like Diarium Pro.
Even where store rules are more flexible, a cross-platform Pro license would still require my own license system with license keys or accounts, purchase validation, recovery flows, fraud handling, privacy/security work, and additional support.
One design goal of Diarium is that it works without a Diarium account. So for now, Diarium will stay with the current model: one-time purchase, no subscription, no Diarium account, and separate purchases per platform/store.
