Having a buckload of code to authorize users on your application is something you may like or not. Speaking for myself I hate it. But I still love rails_admin, here's how you install it without devise. Thanks to phoet for providing the hints in the gist I have forked from.

do NOT add devise

gem "rails_admin", :git => "git://github.com/sferik/rails_admin.git"

bundle install

It works and just does not install devise. You may also want to $ rm config/locales/devise*.

rake rails_admin:install

sed -i.bak -e '/devise/d' Gemfile

In config/initializers/rails_admin.rb:.

require "rails_admin/application_controller"

module RailsAdmin
  class ApplicationController < ::ApplicationController
    private
    def current_user
        nil
    end
  end
end