proposal/mutant/src/java/antlibs/script/antlib.xml

<antlib libid="antopt.script" 
        home="http://jakarta.apache.org/ant">

  <factory classname="org.apache.ant.antlib.script.ScriptFactory"/>
  <taskdef name="scriptdef" classname="org.apache.ant.antlib.script.ScriptDef"/>
</antlib>