MML is a Jetty service (can be turned into a webapp) which handles the service side of the MML-editor. While the latter deals with the user interface, MML is a service that converts HTML documents created by that interface into STILstandoff markup for storage. Also it can convert STIL to MML, so completing the cycle.
The test interface of MML, at /mml/test/editor is a copy of MML-Editor, and supersedes it.