Current maven gpg plugin does not support encrypted passwords in the ~/.m2/settings.xml file. Ticket: http://jira.codehaus.org/browse/MGPG-31. Looking into what it would take for me to add this to the gpg plugin
Integrated in Thrift #134 (See https://builds.apache.org/hudson/job/Thrift/134/)
Closing as this is an external problem that we have no control over and are waiting on fix from maven for this issue.