To be clear: GarageBand is provided by Apple. You should never pay for a DMG file. However, distributing the DMG outside of Apple’s official channels technically violates Apple’s EULA.
: To run versions in the 10.3.x series, users typically needed macOS 10.13.6 (High Sierra) or later. Current versions of GarageBand now require significantly newer hardware, often requiring macOS 14.4 or later . Garageband 10.3.5 Dmg