Since CKAN 2.0, the Recaptcha widget for registration does not appear anymore.

This extension, when activated will re-enable it. 

In order to work:
- git clone https://github.com/Hoedic/ckanext-recaptcha.git
- In your .ini file, add the plugin: ckan.plugins =... recaptcha 
- Add your private and public key: ckan.recaptcha.publickey and ckan.recaptcha.privatekey

You're done (the recaptcha widget might need some CSS improvements however)