Netlify CMS is a self-standing open-source project. We maintain it and are puring a lot of resources into it, because we think it's really important there's a good open-source solution on the market for projects built with static site generators.

However, the CMS itself is not tied to our deployment and automation platform. It can also be setup to work for GitHub pages or self-hosted setups.

The basic idea is that's its an editor friendly content management UI for persisted data stored in a GitHub repository. What you do with that data is up to you.