Another version of creating a server quickly, this on your own desktop machine for development purposes, is described at: https://github.com/openwebwork/WeBWorK_Vagrant. This was work that David did at WeBWorK::Vancouver in June 2013: http://michaelgage.blogspot.com/2013/07/webworkvancouver-june-27-30-2013.html
Notice that you don't need to stay with the default version 2.5.1. As with any server you can switch to a more recent version such as 2.6 or 2.7 following the directions at http://webwork.maa.org/wiki/Github. For the most part you are simply grabbing the newest version of the WeBWork and PG code although on occasion you will need to add a CPAN module or two.
I hope that someone will find time later this semester to create a newer EC2 instance so that one can boot up the most recent WW server almost immediately.