These avatar files are unmodified copies from the Second Life viewer:
  avatar_upper_body.llm, avatar_lower_body.llm, avatar_head.llm, avatar_skeleton.xml

Copyright (C) Linden Research, Inc.
Licensed under the GNU Lesser General Public License, version 2.1.
Source: https://github.com/secondlife/viewer/tree/main/indra/newview/character
Licence text: https://github.com/secondlife/viewer/blob/main/LICENSE