The upcoming major upgrade to the OS X desktop operating-system from Apple for their Mac product lineup named Apple OS X Mavericks got it's sixth "Developer Preview" release. The beta release is now available for download exclusively to registered Apple developers for testing and development purposes only, the beta build is tagged “13A558” for reference. As with every internal/dev-only release their are numerous channels from where non-developers can grab this "EXPERIMENTAL" build (DevUpdateOSX10.9DP6Combo.dmg) as also shared below.

Unofficial download links to Apple OS X Mavericks Developer Preview 6 are shared below, do note that these are untested and are not official so may contain unknown security risks.