The plugin is bound to the generate-resources phase of the build lifecycle. The plugin should be declared at the build section of the pom to trigger the execution
<project>
[...]
<build>
[...]
<plugins>
[...]
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>native2ascii-maven-plugin</artifactId>
</executions>
<execution>
<goals>
<goal>native2ascii</goal>
</goals>
<!-- specific configurations -->
<configuration>
[...]
</configuration>
</execution>
[...]
</executions>
[...]
</plugin>
[...]
</plugins>
[...]
</build>
[...]
</project>