Build Drill with most Maven logging turned off. On every sub-project you will see the following:
The warning is a known issue with Java: http://bugs.java.com/view_bug.do?bug_id=8016153
The RAT folks seem to have done a patch: version 0.12 of the plugin no longer has the warning. Upgrade Drill's pom.xml file to use this version instead of the anonymous version currently used.