OpenSimulator is a 3D Application Server.

It can be used to create a 3D Virtual World (ala Second Life(tm)), and includes facilities for creating custom avatarschatting with others in the environment, building 3D content in world, and creating complex 3D applications in world.

OpenSimulator can also be extended via loadable modules or web service interfaces to build more custom 3D Applications. OpenSimulator is released under a BSD License, making it both open source, and commercially friendly to embed in products.

Although OpenSimulator is still considered alpha software, many people are doing exciting things with it.

Features:

Even though OpenSimulator is relatively young software it already has many useful features

  1. Supports creating 1 or more 256×256 meter Regions, either on a single machine, or linked between multiple machines in grid mode
  2. Extensive ability to customize your avatar, both with custom clothing, skins, and attached objects
  3. The ability to create content in real time in the environment using in world building tools
  4. Real time physics simulation built on top of the ODE physics library
  5. In world application development using a number of different languages, including LSL, C#, VisualBasic.NET & JScript.
  6. 100% free and open source