IPFire is a hardened Linux appliance distribution designed for use as a firewall. This build is based on the pre-existing ARM/Kirkwood port.

Get the IPFire ARM image from the source:

http://downloads.ipfire.org/releases/ipfire-2.x/2.15-core85/ipfire-2.15.1gb-ext4-scon.armv5tel-full-core85.img.gz

Zcat that compressed image to a blank USB stick, 1G or larger. After zcat finishes, put the USB stick into your router.

Clone the ipfire branch of Candyhouse-Linux and build yourself a uImage.

Flash your router with the uImage you just created and watch over your serial port as your router boots IPFire. Setting up IPFire requires a serial connection as it blocks the boot so you can setup the network. There are no defaults.