Editor's update: According to NASA PAO sources there is no ITAR sensitive material in this report online at NESC. What is odd is why they did not issue this report back in 2006 - but rather just released a portion thereof sans correspondence and other items. Oh well.
"NASA has completed its assessment of the DART MIB report, which included a classification review by the Department of Defense. The report was found to be NASA-sensitive, but unclassified, because it contained information restricted by International Traffic in Arms Regulations (ITAR) and Export Administration Regulations (EAR). As a result, the DART mishap investigation report was deemed not releasable to the public. The following provides an overview of publicly releasable findings and recommendations regarding the DART mishap."
Editor's update: Well, here is the full MIB report (or something certainly much longer than the summary that was released) online at NESC. So much for ITAR concerns, I guess.