Working version.

A target pom needs only to include a fragment like this:
<plugin>
  <groupId>org.acmsl</groupId>
  <artifactId>dockerfile-maven-plugin</artifactId>
  <version>latest-SNAPSHOT</version>
  <configuration>
    <outputDir>${project.build.outputDirectory}/META-INF/</outputDir>
    <template>${project.basedir}/src/main/assembly/Dockerfile.stg</template>
  </configuration>
</plugin>

And add a src/main/assembly/Dockerfile.stg such as

group Dockerfile;

source(C) ::= <<
<!
  Defines the rules to generate Dockerfile files.
  @param C the context.
!>
\# wget [artifactoryurl]/<C.T.groupId>/<C.T.artifactId>/<C.T.artifactId>-<C.T.version>.jar
>>