If any kind of mdd to bvh conversion is possible, it would be export or reuse of MacDraft drawings for making 3D animation content in Biovision Hierarchy format. We know that Blender supports export to bvh files, so it's certainly worth trying it out.
Several file types use .mdd extension and actually more than one contains 3D content, so perhaps different conversion exist as well. You can always try to reach out to Blender community for help.
Updated: October 19, 2023