: Open the App Store and check the Purchases tab. If you have ever downloaded Mavericks, it will be listed there for free re-download. Third-Party & Alternative Archives
: If you already have an earlier version of Mavericks (10.9.0–10.9.4), you can download the OS X Mavericks 10.9.5 Update (Combo) directly from Apple Support . Mac OS X Mavericks 10.9.5 Free Download
The official way to download is through the Apple App Store, provided you have previously "purchased" (downloaded) it while it was a current release. While the full installer is no longer easily accessible for new users directly from Apple's main servers, various update packages and archives remain available. Official Download Options : Open the App Store and check the Purchases tab