framework-arduinoteensy-cxx20/libraries/AccelStepper/LICENSE

This software is Copyright (C) 2008 Mike McCauley. Use is subject to license
conditions. The main licensing options available are GPL V2 or Commercial:

Open Source Licensing GPL V2

This is the appropriate option if you want to share the source code of your
application with everyone you distribute it to, and you also want to give them
the right to share who uses it. If you wish to use this software under Open
Source Licensing, you must contribute all your source code to the open source
community in accordance with the GPL Version 2 when your application is
distributed. See http://www.gnu.org/copyleft/gpl.html

Commercial Licensing

This is the appropriate option if you are creating proprietary applications
and you are not prepared to distribute and share the source code of your
application. Contact info@open.com.au for details.