The code and the graphics are in the public domain (CC0). You can use the for personal and commercial projects. Attributions are appreciated but not required.
The background music is made by Kat and published here: https://opengameart.org/content/title-theme-8-bit-style The landing sound is from a soundpack by Little Robot Sound Factory, you can find it here: https://opengameart.org/content/8-bit-sound-effects-library
The font is Russo one, it was originally published here: https://www.dafont.com/russo-one.font