There are several ones (selected only FOSS alternatives, excepting discontinued ones)
- Godot Engine (2D,3D)
- Redot Engine (2D,3D)
- EzEngine (3D)
- Micro Studio (online)
- GB Studio (2D)
- EasyRPG (compatible with the outdated Open RPG Maker)
- Adventure Game Studio
- OHRRPGCE (2D)
- RPG 20XX
- Blitz3D (2D and 3D, Windows only)
- Pixelbox (Html5, Java script)
- RPD JS (Online and all OS)
- RPG Wizard (2D)
- Duality (C#, OpenGL)
- G3D Innovation Engine (3D, commercial quality)
- GemRB (Portable)