mdm — 51 tagged, 20 this year
Mobile Device Management (MDM). A server platform that a company can deploy to centrally manage portable network-connected devices such as the iPhone, iPad and iPod touch. Also applies to MCX/OS X management since Apple Store apps are now as much a part of OS X as they are for iOS.
mobile-device-management — 17 tagged, 4 this year
Also known as MDM, mobile device management is software that helps manage devices for reporting, policy compliance as well as saving labor and standardizing setup amongst many devices when used by the same company or group. iOS MDM uses a framework for device management and often involves third party management software if the company's needs exceed the MDM capabilities of Lion Server.
These are one and the same, even referencing each other in their tag wiki excerpts.
Could the shortened version be made a synonym of the full description?