The demo start-up scripts set:
``` BROOKLYN_CLASSPATH=${BROOKLYN_MARKLOGIC_HOME}/conf/:${BROOKLYN_MARKLOGIC_HOME}/lib/*:${BROOKLYN_MARKLOGIC_HOME}/lib/
```

So logging should be customisable by adding to conf/. At the moment there are no files in conf and Brooklyn should use the logback-custom.xml file in the brooklyn-marklogic module.