In ShowTime versions 6.0 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 in the upper-left corner 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

The Galleria theme currently does not have such a feature, though we are working on it for a future theme release.  In the meantime, if you need a similar option, you can contact us for some suggestions.  Note that this is an advanced customization that may be subject to quote.