The short version

FamilyLegacy stores the core project in a .familytree package on your Mac and does not require a FamilyLegacy account. HighRoad does not receive the project during ordinary local use. Data leaves the Mac only when you choose an export or optional integration such as iCloud snapshots or FamilySearch; model downloads, Apple purchases, and update checks also use the network without uploading the project to HighRoad.