The source code is distributed under MIT license.
All the music in this game was made by Eric Matyas from https://soundimage.org/.
If you want to keep the music for free on your published game, you need to keep the credits for Eric Matyas, on the format specified on his website.
If you want to keep the music, but don't want to attribute Eric Matyas, then you will need to purchase a non-attribution license from he for $30 per track. Please contact him at ematyas@aol.com or access his website for more details.
All the sound effects included are totally free and distributed under CC0 1.0, then you don't need to credit the authors about the sounds.
The sounds are from Freesound Website.