OscarGodson/EpicEditor
EpicEditor is an embeddable JavaScript Markdown editor with split fullscreen editing, live previewing, automatic draft saving, offline support, and more. For developers, it offers a robust API, can be easily themed, and allows you to swap out the bundled Markdown parser with anything you throw at it
License & maintenance
MIT is a permissive license: free to use commercially with attribution.
Last code push 6 years ago.