For those determined to revive a legacy Mac, the community generally agrees on one method: you must find a machine that still has the "Purchases" tab active in the Mac App Store (though this is becoming increasingly unreliable as Apple revokes older certificates). Alternatively, trusted community archives (like the Internet Archive’s software library) often house "unmodified" checksums.
hdiutil detach /Volumes/Install\ OS\ X\ Mavericks hdiutil convert /tmp/Mavericks.dmg -format UDTO -o /tmp/Mavericks.iso mac os x mavericks 10.9 iso and dmg image download
This is the native Apple format. A Mavericks DMG typically contains the "Install OS X Mavericks.app". To use it, you generally mount the DMG and drag the app to your Applications folder. For those determined to revive a legacy Mac,
Mavericks is unique because it is the latest operating system supported by these machines, yet it is modern enough to run 64-bit software comfortably. It is the "Goldilocks" OS for that generation of hardware—lighter than the flashy Yosemite, but more capable than Snow Leopard. A Mavericks DMG typically contains the "Install OS