And the scrubbed version unzips properly as well.
is the one you're talking about, I went ahead and started to download them to check it. The Redump version, mirror source, extracts properly without needing a password. I'm downloading the scrubbed version right now, so I'll get back to you on that one.
GameCube games are compressed using 7z, so, assuming you're on Windows, you need an archive tool capable of unzipping .7z files. 7zip
is a wonderful free option.