To generate the localization report, just add the following in your project's pom.xml:
<project>
...
<build>
...
</build>
...
<reporting>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>l10n-maven-plugin</artifactId>
<version>1.0-alpha-2</version>
<configuration>
<locales>
<locale>de</locale>
<locale>es</locale>
<locale>fr</locale>
...
</locales>
</configuration>
</plugin>
</plugins>
</reporting>
...
</project>
Add a <locale> element for every localization you have.
The report will be generated when you execute the Maven site plugin, like this:
mvn site
You can refer to the generated documentation to discover the different configuration options for the report mojo.