/usr/local/maven/plugins, but
this is dependent on where you installed Mavenmaven mac-package"build.xml file. For instance:
<taskdef name="macPackage"
classname="org.ninjasoft.macpackager.AntMacPackager"
classpath="./lib/MacPackage-0.5.jar"/>
(Ensure that the classpath attribute points to the correct folder
and filename for the MacPackage jar)