OpenSimulator


OpenSimulator is an open-source server platform for hosting virtual worlds and the Metaverse. At one point, it was compatible with the client for Second Life but compatibility has waned for several years.

Features

OpenSimulator is written in C# and is designed to be easily expanded through the use of plugin modules. OpenSimulator can operate in one of two modes: standalone or grid mode. In standalone mode, a single process handles the entire simulation. In grid mode, various aspects of the simulation are separated among multiple processes, which can exist on different machines.
OpenSimulator uses loadable modules for most of its functionality. These loadable modules can be independently developed to add functionality to the server.
OpenSimulator currently uses a modified Second Life protocol for client to server communication, and requires retrofitting to the Second Life client in order to connect. Interoperability with Second Life protocols was once a design goal since 2007. Interoperability with Second Life was no longer a design goal as of OpenSimulator Community Conference 2015. During OpenSimulator Community Conference 2018, the core developers announced they will not maintain compatibility with Linden Lab's Second Life Protocols, and will change them to fix and change whatever they need.
OpenSim has a number of features not available in Second Life. These include that enable saving and retrieval of text data to avatar inventory in notecard format and the creation and management of non-player characters.
OpenSim also uses an architecture known as "Hypergrid", which allows users to teleport between multiple OpenSim-based virtual worlds by providing a hyperlinked map which indexes public grids. This allows for public grids to retain teleportation links to each other without having to be on the same grid. The number of hypergrid enabled opensimulator grids fluctuates. A list of active hypergrid enabled opensimulator grids is maintained by . As of January 2020, there were just over 300 active hypergrid enabled services.