To use the plugin, you've got two options: First of all, it can create a simple text file, called target/rat.txt, with the plugins output. This is done by invoking the apache-rat:check goal.
You may also add a report to the generated site. This is your second option.
To create a text file with the report, you need to run the apache-rat:check goal. Add a section like the following to your POM:
<build> <plugins> ... <plugin> <groupId>org.apache.rat</groupId> <artifactId>apache-rat-plugin</artifactId> <version>0.12</version> </plugin> ... </plugins> </build>
Once you have done that, the plugin can be run from the command line by simply typing
mvn apache-rat:check
An example for running the plugin automatically can be found here.
A section like the following must be added to your POM:
<reporting> <plugins> ... <plugin> <groupId>org.apache.rat</groupId> <artifactId>apache-rat-plugin</artifactId> <version>0.12</version> </plugin> ... </plugins> </reporting>
The report will be created automatically when you generate the site:
mvn site