The first public version of the HTTP API is now live, allowing you to submit render request from within your own applications.
Also new, shorter, host names now exist to access the service, instead of https://maposmatic.osm-baustelle.de/ you can now also use https://print.get-map.org/ and https://api.get-map.org/ , all of these being aliases for the same MapOSMatic instance.
There’s also API documentation, including a few simple PHP example programs, available as HTML and PDF