In their official blog, Cyanogen has posted that they are going to shut down. It is the company behind the Cyanogen OS. Precisely, the company will stop all its operations from the last day of this year, i.e. from 31st December 2016. Developments over nightly builds and its other services will cease from the mentioned date.
CyanogenMod is the open source Android based operating system developed and maintained by the Cyanogen community.
However, CyanogenMod will still exist. It will exist solely for developers who want to continue its development for their personal projects. The CyanogenMod source code will be made available for users who want to continue using it.