To grab the latest Etherpad source code prior to installation it is just one command.
Pre-reqs: git, git-core (possibly?)
git clone git://github.com/ether/pad.git
Done.
You can grab an older version by doing
git log
finding where ye wanna go back to then
git checkout COMMITVALUE ie bd2190f0453f6a189b84b3ff2f1af05d5e023801