How to post and submit data onto a Gravity Form from an external Non-Wordpress site?

I have a Gravity Form on our Wordpress site at URL (http://www.cok.net/literature/vegetarian-starter-guide/).

I'm creating a non-Gravity-Forms form on a different non-Wordpress site, to post and submit data through to this Gravity Form. Is this possible? I'm currently trying to use cURL but no entries are being recorded in the Gravity Form.