I've been wondering about the legality of the CD cover archive. Isn't this some kind of copyright infringement if we upload photos or "art" without the permission of the owner?
If there is someone who disagrees with a cover being present in the Cover Art Archive and owns the rights in it, they can request it to be removed (via a DMCA takedown notice to the Internet Archive). This has only happened a handful of times up to now, though.
Anything that might or might not be a copyright infringement is on Internet Archive's side. MetaBrainz never touch any images that are uploaded to the CAA. As per https://musicbrainz.org/doc/Cover_Art_Archive :
And I’m very glad they shoulder that burden!