Indie game storeFree gamesFun gamesHorror games
Game developmentAssetsComics

you can use it in any project here is a short bit of CC4 (the license).
"You are free to: 

Share - copy and redistribute the material in any medium or format

Adapt - remix, transform, and build upon the material for any purpose, even commercially."

Here is another bit about attribution.
"Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use."

As for dealing with source code, it is generally best practice (in my opinion) to share source code in a "id Software" (creators of doom, quake3, etc) style.

That said as long as you properly denote in your source code the credit it you are covered in the license agreement. Also a link to this asset page would be nice as well.