I put together the following diagram to try to illustrate this:
There are two ways to use Kel:
If you already have a Kubernetes cluster set up, you can just use Kel Layer 1, which provides components on top of Kubernetes that enable developers to define a workflow around managing the operations of their site.
If you don’t have a Kubernetes cluster, you can additionally use Kel Layer 0 which provides tooling around the setup of a cluster specifically for Kel (currently focused on the Google Cloud Platform but eventually multiple infrastructure providers).
While I was heavily involved in the launch, it was more from a project management, process, and promotion point of view. The technical work is all down to @brosner.
While I've been using Kel internally as an end-user (i.e. deploying sites), I haven't had a chance to really dive into the code itself yet so I'm basically a n00b. I plan to record my adventures here.