403 forbidden error while installing Ruby on Rails

[Nethra93]

I am trying to install Ruby on Rails on Windows 8 operating system as discussed in https://github.com/railsbridge/railsbridge-virtual-machine

I successfully installed Virtual Box 4.2 and Vagrant 1.2.7 as mentioned in Steps 1 and 2

As in step 3 when I try to install railsbridge virtual machine by running the below command in my command prompt I get 403 forbidden error.
vagrant box add railsbridgebox http://s3.amazonaws.com/railsbridgeboston/railsbridgevm-3.2-c.box

This is the error I got

Downloading or copying the box...
←[0KAn error occurred while downloading the remote file. The error
message, if any, is reproduced below. Please fix this error and try
again.

The requested URL returned error: 403 Forbidden.

Help me to fix this issue.