It's open sourced : <a href="https://github.com/kapicorp/kapitan" rel="nofollow">https://github.com/kapicorp/kapitan</a>
maybe the sweet spot between helm , which is more a package manager for kubernetes applications;
and kustomize which is a castrated and language specific but limited templating-engine , biggest limitation I've found is the lack of loop for files definition, and also is insufficient for everything that is not included by the language ( because it's very specific to kubernetes definition types )