This version of PowerQuest uses the MIT license, so in short:

You are free to use PowerQuest, for any purpose.
You can study how PowerQuest works and change it.
Games you make with PowerQuest are your own. They do not fall under PowerQuest's license terms and copyright. You're free to do whatever you like with them.
You can share the source code of your own games/content, including sharing PowerQuest files/source code. The only restriction is that you need to distribute this copyright notice and license statement whenever you redistribute it. ie. Don't remove the LICENCE.txt file
This means you can NOT just put PowerQuest up on the Unity Asset Store, as then it would fall under unity's asset store license, not this one, and is therefore forbidden.

MIT LICENSE

Copyright (c) 2021 Powerhoof Pty Ltd

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.