All Google Fonts are released under open-source licenses. You can use them in any non-commercial or commercial project. But in some cases, it may require a Google Fonts API Key to update the font list. If you have a Gmail account, then go here: https://developers.google.com/fonts/docs/developer_api and find the blue button called Get a Key and follow Google's instructions. After you have an API key, insert it inside the template options and click One Click Update.