If you add grails ppa to your sources you still won't install grails. There's no packages ready yet.
Instead of crying you could (temporarily) edit your apt sources and install packages for 12.10 Quantal Quetzal. So do this:
sudo add-apt-repository ppa:groovy-dev/grails
sudo vim /etc/apt/sources.list.d/groovy-dev-grails-raring.list
and change path to
deb http://ppa.launchpad.net/groovy-dev/grails/ubuntu quantal main
sudo apt-get update
sudo apt-get install grails-VERSION
If after typing grails if you press the tab key then it will show all available grails versions from 1.2.5 to 2.2.0 and beyond.
Remember that you can install several versions of grails and switch between them with
sudo update-alternatives --config grails