Ceilometer's goal is to efficiently collect, normalise and transform data produced by OpenStack services. The data it collects is intended to be used to create different views and help solve various telemetry use cases. Aodh and Gnocchi are two examples of services extending Ceilometer data.
Adoption is the percentage of production deployments running the project based on the latest biannual user survey results.
Maturity comes from looking at 5 distinct tags that indicate stability and sustainability. The current criteria includes whether or not the project has an install guide, whether it is supported by 7 or more SDKs, if the adoption percentage is greater than 75%, whether or not the team has achieved corporate diversity and whether or not there are stable branches.
Age is the number of years the project has been in development.