Downloading FLSpacecraft 1.0.0 for Mac from the developer's website was possible when we last checked. We cannot confirm if there is a free download of this app available. The application belongs to Education Tools. This free software for Mac OS X is an intellectual property of Forward Loop Software LLC. We recommend checking the downloaded files with any free antivirus.
From the developer:
The FLSpacecraft application uses physical laws (classical mechanics) to simulate a spacecraft entering and interacting with the Earth-Moon system. The craft is roughly the size and mass of the Apollo Command and Service modules combined, with the ability to fire the Service Module's main engine in short bursts to accelerate and decelerate along the direction of travel.
You may want to check out more Mac applications, such as UN-SCAN-IT Demo, ScienceMatrix or Enzyme X, which might be similar to FLSpacecraft.