Edit: And what if I wrap it with another service, say a CDN, that changed some behaviour and styling (proxying, path rewrite, etc)?
2. I think no, but I believe this is a contentious point, and it depends on whether the "mastodon instance + CDN/proxy/whatever" constitutes a "derived work" or not.
Edit: And what if I wrap it with another service, say a CDN, that changed some behaviour and styling (proxying, path rewrite, etc)?