Hello, I have been working on an addon for Blender to import and export .mu files. It is still very incomplete, but I have released it under the GNU General Public License (version 2), and it is available from github , with documentation here.
NOTE: The addon is now targeted for Blender 2.83. Those requiring 2.79 support should checkout the blender2.79 branch.
NOTE 2: (for Windows) Blender must not be installed in Program Files. Due to file access permissions, installing blender in Pro