Download of Silo 2 2.5 for Mac was on the developer's website when we last checked. We cannot confirm if there is a free download of this app available. We recommend checking the downloaded files with any free antivirus. This software for Mac OS X is an intellectual property of Nevercenter Ltd. The application belongs to Design & Photo Tools.
From the developer:
Silo 2 is a focused 3D modeling application with the ability to effortlessly switch between organically sculpting high-polygon models and precisely controlling hard-edged surfaces. It can be used for anything from creating 3D characters for video games and movies to quickly exploring 3D architectural ideas.
You may want to check out more software for Mac, such as VectorGeddon, which might be related to Silo 2.