This is the (properly, an) Emacs major mode for the Groovy programming language.
Groovy is a programming languages and all programming languages need an Emacs major mode. This is the currently maintained Emacs major mode for Groovy.
This site provides the official release download for the Emacs Groovy mode, as well as being the mainline in version control for developers and for those users who prefer continuous update rather than release-based update.
(And yes, it probably would have been better for this project to have been called Emacs Groovy Mode.)
This project has now shifted to using Git on GitHub. See https:/