This plugin takes the approach of providing a native Language Server Protocol implementation based on an (in-process) Ensime library. There is only minimal code written in Typescript to hook the language server into the plugin, and plans are to move that to Scala.js, so this should be a 100% Scala implementation.
Head over to the repo:
to help out!
The ensime-atom gitter room is probably the best place to start asking questions.