OnePlus One users might be waiting for the new Lollipop based ROM for their smartphones. OxygenOS comes with stock Android UI, and also adds some new custom features, such as Clear Image, and lock screen gestures. The update has been developed by the company with the help of developers from the Paranoid Android team. The news disappointed many OnePlus customers, including me, who were looking forward to their Lollipop updates, but the update is now ready for downloading from the OnePlus servers. It is based on Android 5.0 Lollipop.
Source: https://thehackernews.com/2015/04/download-oneplus-oxygenos.html