With all due respect, I think the title of this post should be amended as this is not Open Source.
After perusing the Github repo, it looks like the actual editor logic is not open source (in fact it lives in a private repo which you control), and the linked repo is just a wrapper around it.
After perusing the Github repo, it looks like the actual editor logic is not open source (in fact it lives in a private repo which you control), and the linked repo is just a wrapper around it.