- works on Linux, Windows and Mac (or HTML5)
- has some kind of editor
Engines I know and use
- Godot - feature packed, powerful, easy, awesome, one and only
- Atomic - looks like Unity clone
- Bitsy - little editor for little HTML5 games where you can walk around and talk to people.
- Bladecoder - Classic point and click adventure game engine and editor
- Blender Game Engine - built in into Blender - 3D creation suite.
- Catroid also known as PocketCode is similar to Scratch but it allows creating games on Android device
- Game Editor - I don’t know what to say about this one. It looks pretty old school and cool at the same time. Just take a look
- Game Pencil Engine - multi-platform 2d game engine in development
- GDevelop - it seems to be engine in style of Construct and Multimedia Fusion: uses visual programming and it’s quite easy to get started
- Ink - interactive narration engine with export to HTML5 and json
- LIKO-12 yet another fantasy console
- MegaZeux - MegaZeux is a game creation system originally released in 1994 and still being developed today.
- nano JAMMER - nano JAMMER is a fantasy console for tiny games with a single page of source code. It is perfect for tweetjams and hobby coding on a busy schedule.
- Playscii - ASCII art editor and game engine
- PuzzleScript - HTML5 engine for writing tile-based puzzle games
- PX8 - open source implementation of PICO-8 fantasy console.
- Ren’Py - visual novel engine
- RPGBoss - similart to RPG Maker
- Scratch visual programming environment. Designed to help kids learn programming. There is also more advanced variation of Scratch called Snap
- script8 - JS based fantasy console, records your game on tape (URL), has a time-traveling debugging tool
- Solarus - 2d engine for creating Zelda like RPG games
- Superpowers - for creating 2d/3d games in HTML5.
- Torque 3D - 3d game engine
- Twine - tool for telling interactive, nonlinear stories
There is handy list by paladin-t. Some of them are FOSS.