The Scalate War Overlay is a feature of the maven war plugin which allows you to depend on a WAR in your maven dependencies.

The war plugin then copies all the contents of the war overlay into your web application. This saves you copy and pasting various shared resources and templates across web applications.

For example to use the Scalate WAR overlay in any maven web application just add this section to your pom.xml

<dependencies>
  ...
  <dependency>
    <groupId>org.fusesource.scalate</groupId>
    <artifactId>scalate-war</artifactId>
    <version>1.4.0</version>
    <type>war</type>
  </dependency>
  ...
</dependencies>

Note that if you are already using one of the scalate archetypes you don't have to worry about this; your archetype is already setup correctly for you.