I may be stupid for not knowing this but, what does CCO stand for?
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Cc0 stands for Creative Commons Zero, I can't remember the exact details but it basically means that you can do whatever you like with these assets, you don't even have to give credit :)
the only requirements from my side is you don't try sell these assets on another site or claim them as your own, other then that feel free to do as you wish :D
hope this helps, enjoy ^^