One of the best features of the Android operating system is the high level of customizability and flexibility you get on the kinds of software you can run. In addition to apps from the Google Play Store that can take full advantage of phone hardware, the Android community has made all kinds of custom ROMs, like CyanogenMod, that users can flash to their devices.
The OnePlus models, and a few other phones, use custom versions of CyanogenMOD, called Cyanogen OS, that is updated and managed by Cyanogen Inc., and also includes a suite of custom apps not found on CyanogenMOD. As of yesterday, though, the company announced that it will be offering the custom apps suite to any users running an updated version of the CyanogenMOD operating system.
Because of the open source nature of CyanogenMOD, anybody can choose to install the operating system on their Android phone, but previously you would not have access to these Cyanogen OS apps, called the C-Apps package. The company notes that once you are running CyanogenMOD, the C-Apps package will be an optional download that you can get from Cyanogen’s website.
The C-Apps package includes a custom theme store and per-app theming options, AudioFX, Cyanogen Accounts, Gallery, Dialer with TrueCaller integration, and Email powered by Boxer. If you’re running CyanogenMod 12.1 and your system is fully up to date, you can head to the CyanogenMod website to learn more and to find download links.
Source: CyanogenMod Blog