Great news for you flashaholic owners of the OnePlus 3. CyanogenMod 13 is now officially available for the OnePlus 3 and nightlies are now up for you to download and flash. Interestingly, CyanogenMod was the first provider of software for the OnePlus One. Shortly after that, CyanogenMod and OnePlus parted ways, forcing OnePlus to develop its own Oxygen OS'. CyanogenMod 13 is an alternative OS firmware that can replace the factory firmware on your smartphone. If you'd like to install the OS, you'll need to have your bootloader unlocked, and you need to have flashed an alternative recovery...
Source: http://www.gsmarena.com/cyanogenmod_13_for_oneplus_3_now_official_nightlies_available_-news-19628.php