The MIT license just gives you permission to use the work as published. Normally that work would be in source form, but there is nothing in the MIT license requiring that. In this case, it seems that the authors chose to release the binaries under the MIT license.
It was originally an internal tool, so I would guess either A) he doesn't have permission from all the contributors or B) he used reused code from elsewhere within Microsoft that wasn't open source compatible.
