I wrote a small plugin that lets you set the default settings for Gravity Forms across an entire WP Multisite (Network). The settings are specified in wp-config.php, and once you set them there, users of individual blogs won’t be able to override them.
Install this plugin into the /wp-content/mu-plugins/ directory of your multisite, and then put this in your wp-config.php:
/* Global settings that will be active across the multisite */ define('GF_DISABLE_CSS', 0); define('GF_OUTPUT_HTML5', 0); define('GF_NO_CONFLICT_MODE', 0); define('GF_RECAPTCHA_PUBLIC_KEY', ''); define('GF_RECAPTCHA_PRIVATE_KEY', ''); define('GF_LICENSE_KEY', '');
Read more info about the plugin on GitHub!