While Apple no longer lists Mavericks prominently on the Mac App Store , there are still ways to secure an official installer:
If you have a friend with a functional Mavericks USB: mavericks os x 10.9.x dmg
Disconnect from the internet, open Terminal during the installation process, and change the system date to a time closer to the OS release (e.g., date 110113002013 for Nov 1, 2013). Fixing Attributes: While Apple no longer lists Mavericks prominently on
: If you previously "purchased" Mavericks (even for $0), it remains available in your tab on older Macs. Internet Archive : Community members have uploaded verified Mac OS X 10.9 Mavericks Installers 10.9.5 ISO/DMG files for preservation. Spiceworks Community How to Create a Bootable USB from the DMG open Terminal during the installation process