Kubeless is built on top of Kubernetes from scratch and is making use of the core Kubernetes primitives (e.g. deployments, services, confimaps, ingress) to avoid re-inventing the wheel. In addition, Kubeless makes use of Prometheus for monitoring functions calls, which is built directly into the runtimes.
Gitkube is tool for building and deploying docker images on Kubernetes using git push.
After a simple initial setup, users can simply keep git push-ing their repos to build and deploy docker images to Kubernetes automatically. It can be configured to update any k8s deployment with a newly built image using dockerfile present in the repo.
LastBackend is a whole ecosystem of products and it allows, not only to manage containers similarly to Kubernetes but also collect their images on github/bitbucket/gitlab from the source code. It also contains a whole complex of infrastructural services designed to speed up developing, testing and deploying releases.