Apache Camel was created before github existed. The project is hosted at ASF on their infrastructure.
ASF integrated with github 4-5 years ago and all their projects are mirrored to github.
For example the first PR at github to Apache Camel is from November 2012.
At github projects can be starred by users whom seems to like the project.
On the 9th November 2016 Apache Camel reached 1000 stars at github.
A few days later Apache Camel has 1040 stars.
Thank you for showing the support for the project.