They (more than likely) are python scripts so the install step is copying to the addon folder. Haven't looked into the blender thing in a while but someone cou

They (more than likely) are python scripts so the install step is copying to the addon folder. Haven't looked into the blender thing in a while but someone could use the generated C++ API to create an addon and make it difficult to install but who knows if anyone (other than cycles) uses it.