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
: This platform hosts Apple OS X Mavericks (10.9.5) as a 6.1GB disk image for historical preservation. Mac OS X Mavericks 10.9.5 Free Download
Before downloading, ensure your Mac is compatible with 10.9.5: Download OS X Mavericks 10.9.5 Update (Combo) The official way to download is through the