'The Solar System - Explore' is currently in the middle of being re-designed and created using the latest version of the Unreal Engine. The release date is not clear as this project is not managed by a large team, nor is it backed financially. It is a project that I (Christopher Albeluhn) am doing on my spare time. Release dates will become available when they are known, and information will be updated both here, and on our Facebook page.
I would like to personally thank everyone who supported the original version of this software a few years back through 'Kickstarter'. You made the initial drive of the software possible. Even though it's not available for purchase anymore, once the new version is done I will be providing all those backers with a free copy of the updated version.