OpenSimulator is a 3D Application Server. It can be used to create a virtual environment (or world) which can be accessed through a variety of clients, on multiple protocols. OpenSimulator allows you to develop your environment using the technologies you feel work best – we’ve designed the software to be easily extendable through loadable modules to build completely custom configurations. OpenSimulator is released under a BSD License, making it both open source, and commercially friendly to embed in products.
Out of the box, OpenSimulator can be used to simulate a virtual environment similar to Second Life™ (including client compatibility). Other environments, protocols and features are supported via add on modules.