They had to release some (I believe most) of the firmware.
Check it out here:
http://www.archos.com/support/download/software/gpl_notice.html?country=global&lang=enFrom the README:
The Archos 404, 504, 604 and 604WIFI products include some Free Software
programs which are copyrighted by the Free Software Foundation and others
and published under the GNU General Public License (GPL) and Lesser
General Public License (LGPL).
In compliance with the GPL and LGPL, we provide the source code of these
programs for download.
Maybe very helpful? Dunno.