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If it did not start, download RayTask.dmg.
RayTask is not notarized by Apple yet, so macOS asks you to confirm it once. It takes about 30 seconds.
Open RayTask.dmg from your Downloads, then drag the RayTask icon onto the Applications folder.
Open RayTask from Applications or Launchpad. macOS shows a warning. Click Done, not Move to Trash.
Open System Settings → Privacy & Security, scroll down to Security and click Open Anyway next to RayTask. Confirm with your password or Touch ID. The button appears for about an hour after step 2; if it is gone, open RayTask again.
Open Privacy & SecuritymacOS asks one last time. Click Open Anyway. From now on RayTask opens like any other app, and updates install from inside it.
Apple’s notarization costs an annual developer fee, which RayTask will pay as the project grows. Until then, opening the app this way is the procedure Apple itself describes: Open a Mac app from an unknown developer. RayTask works on your Mac only and never uploads your photos.