Maybe I can ask for clarification on Newgrounds’ own forums on their stance on stuff like Cascadeur. I do know the Art Portal rules of that site say to avoid even using a lot of pre-made or kitbash assets in my 3D art submissions, or at least not use them as the main focus of my render (it’s probably fine if I just use pre-made assets for set dressing behind the main character, at least). I do know using software that kind of does a lot of the work for you (even if they’re old), like Windows Movie Maker 3D or Source Filmmaker, is a bit dicey and of course you would get bullied off the site entirely if you use the infamous “GoAnimate” website for “animation.”
Won’t know until I ask the right people, I guess. I’ll go do that now…