Board Thread:Geometry Dash Update Discussion/@comment-25213373-20150418140925/@comment-25651575-20180606170707

Before this thread is inevitably closed, I'm gonna leave a link to LockForums as a possible solution to preventing necroposting.

To answer your question, the NG rules are that if it isn't your song, you don't upload it. It doesn't matter whether it's under a Creative Commons license (which is still technically copyrighted) or even if it's in the public domain, nor does it matter if the creator gave you full written permission - you don't upload it if you didn't create it, end of story. Of course, all this is detailed in the Newgrounds audio guidelines.