Comment 6 for bug 940063

I've been digging a little deeper.

"iscan" is freely downloadable from here:
http://linux.avasys.jp/drivers/iscan/2.28.1/

The source code is also available, and the readme clearly states that this software is GNU GPL2

If you take a look, there's even an updated version that depends on libltdl7 (available in 12.04):
iscan_2.28.1-3.ltdl7*

I don't know why avasys has not updated their site to distribute this version.

Jockey added the driver repository in /etc/apt/sources.list.d/jockey.list:
deb http://linux.avasys.jp/drivers/lsb/epson-inkjet/stable/debian/ lsb3.2 main

I don't know why avasys has not made a repository for other packages like iscan.

Updated procedure to enable scan over Wifi for Ubuntu 12.04(+):

1. Use jockey to install the ESC/PR driver (enables print over Wifi, installs device, etc)
2. Download the following (for amd64, use i386 for legacy systems):
http://linux.avasys.jp/drivers/iscan/2.28.1/iscan_2.28.1-3.ltdl7_amd64.deb
http://linux.avasys.jp/drivers/iscan-data/1.13.0/iscan-data_1.13.0-1_all.deb
http://linux.avasys.jp/drivers/scanner-plugins/iscan-network-nt/1.1.0/iscan-network-nt_1.1.0-2_amd64.deb
3. Install those with dpkg
sudo dpkg -i iscan*
4a. Add this line to /etc/sane.d/epkowa.conf (use your printer's IP)
net 255.255.255.255
4b. Another, untested, possibility:
net autodiscovery
5. Comment out this line in /etc/sane.d/epson2.conf (just in case)
#net autodiscovery
6. Restart saned
sudo /etc/init.d/saned restart