Note: do not expect lightning performance and/or have a list of dozens of MB for url_filter (specifications recommended minimum 256Mb of ram and the DS has 128), but it works!
Ingredients: :)
1) DS with patched uboot to load the OS from usb pendrive.
2) access to the serial console of DS: is necessary to the first set up of ipfire, then just use the gui).
3) an ethernet port usb (I found one on ebay for 7 € ss included).
4) a usb pendrive.
Preparation :)
Download
ipfire-2.13rc2.1gb-ext4-scon.armv5tel-full-core65.img.gz (scon = serial console) and prepare the usb pendrive with it.
The image will create two partitions on usb pen: sdX1 in fat with files of the boot loader and the kernel, sdX3 with ext4 rootfs (the distro).
Plug the usb pendrive and copy both partitions to a folder on your pc.
Once you have copied the 2 partitions, recreated with fdisk a new pendrive filesystem (according to a scheme compatible with the Dockstar uboot) sdX1 as ext2 and sdX2 as swap, both formatted.
At this point, copied to sdX1 the rootfs previously saved (ex sdX3), create in it the /boot folder and copy all files named "kirkwood" (System.map, config, vmlinuz), also copied in the /boot folder uImage and uInit (to be renamed in uInitrd).
In the folder /etc of the pendrive (sdX1) modified fstab, adding the mount point for / , the swap partition and removing the mount for the fat partition (which no longer exists).
The pendrive is now ready. Insert it into a usb port on the DS, connect the serial port of the DS with an adapter and made the first ipfire configuration.
regards
p.s. sorry for my bad english I translated the message from an Italian board :)