Update to previous post: I've emailed the license holder for the music used in my short animation. (Hopefully I haven't got any of this wrong). They informed me that buying a license isn't neccessary in terms of uploading the video to youtube and recommended that I upload it there, than "embed it into Newgrounds" as opposed to getting a license to upload it here. So that's what I'm gonna be doing:
It's not what I would of have prefered but it is what they said I should do, and I guess it saves me money which is a plus especially nowadays.
(If there's anything wrong or some issue with what I've written above, I would like to know - I don't want this to linger over me for the foreseeable future).
also thank you @seth