The older script version wasn't compatible with STS "Grails Dependency Management".
This version also downloads sources and javadocs of transitive dependencies.
Quick start:
grails install-plugin eclipse-scripts
grails compile
grails download-sources-and-javadocs
grails sts-link-sources-and-javadocs
After this refresh the workspace in STS (F5), restart STS and do "right click on project name" -> Grails Tools -> Refresh Dependencies.
Go to the plugin page for more information.