To anyone else lured in by the "Ubuntu 12.04 (.deb)" install option - you need to add the playdeb repository to your sources list for the big "install this now" button to actually work.

Either install this package: http://archive.getdeb.net/install_deb/playdeb_0.3-1~getdeb1_...

Or otherwise add the repository to your apt sources:

  $ cat /etc/apt/sources.list.d/playdeb.list
  deb http://archive.getdeb.net/ubuntu precise-getdeb games

Then do apt-get update (or equivalent) and the install link will work. As would just installing the warsow package, by that point.

I'm a little surprised they didn't mention that on the page.