The GPL (and other FOSS) sources from Archos have been checked into git for convenient patching and access:

 http://gitorious.org/archos-buildroots/gen7

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 2.6.37.2 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
and  http://bug10738.openaos.org/images/archos_gen7/37/zImage