ApolloStation is a community-driven SS13-derived codebase aiming to evolve the genre. Though specifics are sparse in the repo itself, it builds on SS13 principles with an emphasis on modularity and maintainability.
The time of Archmages will be an open-source MUD game.
Players can be connected to the game server using either a special client or through IRC or they can use a Web-interface. This means that a player can reach the server from virtually any platform.