All of SweetHawk's Zendesk apps come with a 14-day free trial.
When installing a paid app, Zendesk's marketplace functionality is to always ask for credit card details. However, we, in fact, don't bill you for the first 14 days. So if you uninstall the app within 2 weeks, you won't get charged.
If you need to test out the app for a longer period of time on your Zendesk sandbox, contact us at email@example.com