As I wrote above only the discid.dll is needed. If you also copy the other files no harm is done, though.
I assumed you are running Picard from source as discussed in Is there an estimated release date for the next Picard? - #9 by Weblate. Then the source directory is where you have Picard’s source checked out.
Maybe it would be simpler for you to run a daily build from GitHub - phw/picard-daily: Inofficial daily development builds for MusicBrainz Picard
The error message is pretty clear. That’s an internal error on some of the archive.org servers. Not much to do about this.