ActsAsMailBalancer is a rails plugin that sends ActionMailer messages using different user accounts to enable you send huge number of messages per day.
This is what rails says:
DEPRECATION WARNING: You have Rails 2.3-style plugins in vendor/plugins! Support for these plugins will be removed in Rails 4.0. Move them out and bundle them in your Gemfile, or fold them in to your app as lib/myplugin/* and config/initializers/myplugin.rb. See the release notes for more on this: http://weblog.rubyonrails.org/2012/1/4/rails-3-2-0-rc2-has-been-released. (called from <top (required)> at /var/www/episodecalendar.com/Rakefile:7)