While Apple does not host Leopard on the main App Store, they still maintain a Knowledge Base article for older software. It is always worth checking the official Apple Support downloads page. However, for an OS as old as 10.5, these links are frequently dead or point to update packages rather than the full installer.
While Apple effectively considers older OS versions "legacy," they are technically still copyrighted software. Official download links were removed from the Apple Servers years ago. This has pushed users toward "abandonware" sites, which are often riddled with broken links, corrupted files, or potential malware.
Mac OS Leopard, also known as Mac OS X 10.5, was the sixth major release of Apple's Mac OS X operating system. It was a major update that introduced several innovative features, including: