BlackBerry MDS (Mobile Data System) is a development framework for BlackBerry that allows developers to use Visual Studio as a platform and use what RIM calls a RAD (rapid application development) method. The RAD development method involves a drag and drop interface where you can then create the code behind your forms to do the work.
This news comes after RIM announced new plug-ins for Eclipse and Visual Studio. It seems that RIM is focusing on the Java and web development platforms so platforms such as MDS are all getting canceled.
As of December 31st,2009, both BlackBerry MDS Runtime and Studio will no longer be available. Runtime and Studio will lose support as of June 30th, 2010.
[Thanks for the tip J.M.]
UPDATE: Official notice from RIM.