Post by William Ritson in What assets we can use??

Can I use other people’s work in my game?

Yes, but only if:

You obtained it legally (e.g. you downloaded free assets from the Unity store, you bought a font from a graphic design website, etc.).
The author/creator has given you their permission, in writing, to use their work in your game.
The work (such as music, art, etc.) has a Creative Commons license attached to it or is known to be in the public domain. If you’re not sure what these terms mean, spend a little time reading about copyright in advance, so you know how to identify and use this work. There are many, many websites and search tools for finding free (and 100% legal) art, music, and so forth. They are great to use in a pinch if you don’t have the time or desire to create your own assets.

itch.io