gistfile1.rb

mime :json,   'appliaction/json'

post '/update' do

  inviters = {

    :yodapunk => {
      :count  => 0,
      :link   => 'http://vk.com/reg198193',
      :select => true
    },

    :kossnocorp => {
      :count  => 0,
      :link   => 'http://vk.com/reg37829378',
      :select => true
    },

    :porqz => {
      :count  => 0,
      :link   => 'http://vk.com/reg668467',
      :select => true
    },

    :elv1s => {
      :count  => 0,
      :link   => 'http://vk.com/reg1114384',
      :select => true
    }
  }

  referer = :yodapunk

  content_type :json

  {
    :latest_version => {
      :number   => '1.9',
      :link     => 'http://widgets.opera.com/widget/15872/'
    },

    :vk_referer => inviters[referer][:link],

    :promo => {
      :text     => '',
      :lang     => '',
      :number   => 0,
      :until    => Time.now
    }
  }.to_json
end

1st line: 'application' instead of 'appliaction'

я не виноват, это коснокопр писал! ;))