Free to play, free to learn from, free to build on.
Everything here is meant to be used, not just looked at. There are two licences, because code and creative work are different things and the world licenses them differently.
The software, meaning everything that makes the games run, is under the MIT License. Do what you like with it: read it, learn from it, copy it into your own project, sell what you make. The one condition is that you keep the copyright notice.
The creative work, meaning the game designs, the words on this site and inside the games, the pixel art, the music and the sound, is under Creative Commons Attribution-ShareAlike 4.0. You are free to share it and to build on it, for any purpose including commercial, on two conditions:
That second condition is the whole point. It means the work stays open. Nobody can take it, wrap it up and close it off again.
To credit the game, this is enough:
“UPHILL: Sierra Nevada Fire Rescue” by Uphill Games (uphill-games.com), licensed under CC BY-SA 4.0.
The full terms live in the repository, in LICENSE for the code and LICENSE-CONTENT for the creative work. If a use does not obviously fit either, ask: hello@uphill-games.com.