The documentation for Mojo's Maven Plugin for GWT is here: https://gwt-maven-plugin.github.io/gwt-maven-plugin/

NOTICE There is a new plugin (archetypes and eclipse integration), a fresh start that correctly support multi-module projects, it is not version-bounded with GWT, support multiples GWT versions and other fixes, improvements and best practices. This plugin is now considered the legacy GWT maven plugin (aka mojo GWT maven plugin) and the new one is considered the new generation GWT maven plugin (aka tbroyer GWT maven plugin). The legacy maven plugin is still supported but it is strongly encouraged to use the new one for new projects.