VESTA is described as '3D visualization program for structural models, volumetric data such as electron/nuclear densities, and crystal morphologies' and is an app in the Education & Reference category. There are three alternatives to VESTA for Linux, Mac and Windows. The best alternative is Avogadro, which is both free and Open Source. Other great apps like VESTA are Jmol (Free, Open Source) and Rasmol (Free, Open Source).
RasMol is a computer program written for molecular graphics visualization intended and used primarily for the depiction and exploration of biological macromolecule structures, such as those found in the Protein Data Bank.