You may develop your project with your Sitefinity Downloadable and Sitefinity Cloud trials. After your trial period expires, you must purchase a license to continue with your development. After you purchase a license, you can apply the new license file to the trial project and continue with your development and project launch. For more details on how to use the license key to your Sitefinity project, please refer to the "Activating a license" section of the Sitefinity Documentation.