Due to frustrations with the amazon mp3 store’s mandatory (well, for albums anyway) download client not being installable on Fedora 14, I have reverse engineered the AMZ file format and am working on a library and download tool for the AMZ files distributed by Amazon. This code is in under the ISC license and will allow you to download from amazonmp3 anywhere that glib and libsoup work.
Note: This does not allow you to get MP3s for free. It only allows you to download MP3s you have bought, as you have to have proof of purchase (e.g. the AMZ file that they give you).
I intend to write a GTK+ frontend soonish, but a usable commandline client was better than nothing. You may download the code from my mercurial repository by doing:
$ hg clone http://hg.atheme.org/users/nenolod/libamz $ cd libamz $ sh autogen.sh $ ./configure $ make $ sudo make install
You can then use amzdecrypt to view the raw underlying XSPF playlist, amzls to view a track listing and amzdl to download the music referenced by the AMZ file.
Have fun!