In ShowTime versions 6.0 and Galleria versions 2.1.2 and above, there is a setting to automatically hide the pricing and "add to cart" buttons for products that are priced at $0.  To access this, please follow these steps:

• Within your Shopify dashboard, click Online Store > Themes > ShowTime
• Click Customize theme
• In the theme editor browser, click the Theme settings tab link at the bottom of the screen and click on the Free products heading
• Here you can specify the text that should appear for products that are $0, and there is a checkbox to hide or show the cart button

With this feature enabled, the price will be replaced with the text you specified and the cart button will be hidden throughout the theme.