OpenMW is an open-source open-world RPG game engine that supports playing Morrowind.

Retro RPG Game Maker

Unreal Engine 4 Action RPG type game starter kit.

An implementation of the Diablo 1 game engine

H2服务器引擎架构是轻量级的，与其说是引擎，个人觉得称之为平台更为合适。因为它封装的功能少之又少，但是提供了非常简洁方便的扩展机制，使得可以用C++、python、lua、js、php来开发具体的服务器功能。H2引擎的灵感来源于web服务器Apache。

RPG Map Maker

Old-school CRPG engine, editor and game

Script per la creazione di Giochi di Ruolo "Play by Chat" su browser

Open Source role-playing game engine for Taleworlds' Mount&Blade Series written in C# using Ogre3d Engine

Js JRPG Engine for FGMK

A tech demo for a browser-based, Pokemon-esque RPG overworld engine that even supports Internet Explorer 6.

A RPG Engine using JavaScript

A library with generic and usual role playing games features.

A modern, web based, procedurally generated MUD.

An open source CRPG system.

AgoraMUD is a simple MUD (Multi-User Dungeon) written with Python 3.

JHeroes CRPG engine and Heroes of Hawks Haven

Text-based browser roleplaying game built in Unity. Currently working on significantly more updated fork https://github.com/lizard-entertainment/runityscape. Don't fork this one!

A text-based RPG battle engine for java

Fun little HTML+client-side JS RPG engine

Main repository to house several examples of games using the web-rpg-framework.

The version IDMarinas Edition is based on the version 1.1.2 Dragonprime by Dragonprime Development Team (Dragonprime) and have code of Oliver Brendel (NB Core).

an ARPG, dungeon crawler open world engine in ruby to replace SaaS bootstrap-like interface

Role-playing game engine using the LWJGL 3.

Body and Brain - Simple Role Playing System

A framework for making top down old-fashioned RPGs in Flutter. Currently this is based on the Flame engine.

Small Python RPG Engine. Features will be added when I take the time.

Basic 3D engine