I found the file
setup-ubuntu-armhf-3.8.13-bone30.sh, which appears to do closely related things, i.e. start dhcp server, start gadget, etc.
How is this file used?
I am guessing it was executed on a Beagle running from sd card with this image, and after shutdown, the sd card image was copied
to a file (using dd, etc.), from where it was posted on the web.
My reason for wanting to change the ip address is that my desktop ssh is complaining about the change of remote host key
every time I switch to another image, e.g. angstrom.