For "there is no Workflow to setup" -- I think installing a full app is way harder than setting up Github workflow. Sure, for a test usage you can press "deploy to heroku" button, but for a production use you'll want monitoring, security patching, disaster recovery, user authentication... And github gives you all that automatically.
(I'd say differently if you had a large amount of data or a large number of editors... but it seems you only have just over 5000 items and few updates a month, so this will easily fit into a single git repo)
Re "the editor is generated based on the JSON schemas." -- this sounds really interesting! Looking at the public instance I only saw a way to view the data and it was pretty plain, just syntax-highlighted JSON.
If there are some JSON-specific editors, I suggest putting some screenshots in README or on the website somewhere so people can appreciate your work!
And yes, there is an API, which is already integrated with tools such as MONARC (https://github.com/monarc-project/MonarcAppFO).
The API is really easy to use. There is also a client: https://github.com/CASES-LU/PyMOSP
Versioning is planed for the next release.