it's open source. i figured why rewrite the whole framework if it already exists. same for php, why write your own forum if you can just use phpbb.
i have made lots of updates though and written everything else on the site...items, compounds, manufactures, monsters, locations, tools, different security groups...etc.
i don't use php. ruby on rails is it's own programming language. the code is actually written in ruby with the rails framework for web programming.
check out http://www.rubyonrails.org/screencasts and watch the first screencast to see how cool it is.
there is also lots of videos at http://railscasts.com/ if you are interested in learning ruby on rails.
it's much more fun to program with then php or perl.