Welcome to the org.
We are indeed a place where people can upload their AMVs...a great place to do so if you ask me (Of course my opinion on this matter is completely unbiased
) However, we're more than just that. We're a community dedicated to all things AMV (critiques, techniques, theory, anime, music, and more).
If you want to ask an editor for permission to upload on another site, go for it. That's something better suited for a private message though. If you aren't quite sure who the creator is, you can try finding them using supersearch
or one of the other search methods in our swiss army search-knife