io_scene_md3.zip (8.2 KB)
Above is the zipped version of the addon. I got it from github: https://github.com/neumond/blender-md3
When I install from file, you can “activate” this addon in User Preferences. However, when you go to File->Import, the option for importing md3 files is missing. I looked at Blender’s console and it shows no errors, only a “successfully installed” message.