A lightweight, free and open-source game engine for Action-RPGs.
Solarus is a free and open source Action-RPG game engine, licensed under GPL, and written in C++.
It runs games (called quests) written in Lua, and can work on a great number of platforms.
Solarus also features an editor application to help you create your own quests.
A collection of Solarus Quests can be explored in the Solarus website:
Information about Solarus and making quests can be found in the Solarus communities: