Is the data available via a RESTful JSON API? If not is that something that would be possible, more than willing to help.

The data would be very useful to mobile apps and mashups if presented in an API.

yes it is. you have a read API being built at http://world.openfoodfacts.org/data and a basic write one at http://en.wiki.openfoodfacts.org/Project:API If you'd like to help improve it, send a mail to pierre at openfoodfacts dot org so that i can invite you to our Slack.