Builds and dependencies are managed with Gradle.
./gradlew shadowJar builds a jar that includes all dependencies (using Shadow) under build/libs/services-javascript-all.jar.
This repository depends on services-base-java, which is referenced relatively in settings.gradle. You need to clone services-base-java separately and place it on the same level as this repository, so that it can be referenced with ../services-base-java.
Start services with ./start.sh.
Setup your favorite IDE, then run or debug the JavaScriptServices.java class and set the CLI arguments to the ones used in the start.sh script.
After cloning, use the Import Project or File -> New -> Project from Existing Sources... feature and select the build.gradle to start the import.
For any subsequent Monto language services, use File -> New -> Module from Existing Sources....
Make sure you have a up-to-date Buildship Gradle Plug-in installed. At the time of writing Eclipse 4.5.2 (Mars 2) is the newest stable Eclipse build. It ships with the Buildship Gradle Plug-in version 1.0.8, but you will need at least 1.0.10, because of these changes. To update Buildship, use the Eclipse Marketplace's Installed tab.
After cloning, use the File -> Import -> Existing Projects into Workspace feature and select the cloned folder.