ACP, One of the Oldest Open Source Apps
Esther Schindler writes "The Airline Control Program (ACP), introduced by IBM around 1967, predated the term 'open source' by decades. But you may be surprised by how much of its development resembles the FOSS movement today. The ITWorld.com article An Abbreviated History of ACP, One of the Oldest Open Source Applications describes what made it special."
Perhaps they were following the precedent set by the Valerie Plame case and assumed that it was OK to out covert CIA officers.