The GPL (and other FOSS) sources from Archos have been checked into git for convenient patching and access:
There are efforts underway to get different kernel versions running on this hardware, e.g. nicktime has http://gitorious.org/archos-linux/.
Notes and status on Nicktime's 126.96.36.199 kernel
You can try this kernel out with any image from http://bug10738.openaos.org/ at /images/archos_gen7/37/
Untar image as root to internal flash, e.g. if device gets mounted on /media/ARCHOS5:
cd /media/ARCHOS5 sudo tar -xJf path/to/image/image.tar.xz
update menu.lst with http://bug10738.openaos.org/images/archos_gen7/37/menu.lst
flash new http://bug10738.openaos.org/images/archos_gen7/37/initramfs.cpio.gz