OpenSim: Free & Open-Source Virtual World Platform - Create, Share & Experience 3D Worlds

OpenSim is a free and open-source virtual world software platform designed for creating, sharing, and experiencing 3D virtual environments. It's similar to Second Life but provides greater flexibility and customization options. OpenSim allows users to create and customize their own virtual worlds, avatars, and objects using a variety of tools and scripting languages. It also supports multiple users, enabling collaborative experiences and social interaction. OpenSim is used for a variety of applications, including education, training, gaming, and social networking.