Game frameworks/engines under Zlib license

This software is provided 'as-is', without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software.

Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.

TLDR: You're not forced to put a License.txt in any part of your game when you distribute it. You're free to decide whether you credit them or not.
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LÖVE (2D)- https://love2d.org/ (Lua)
LÖVE is an *awesome* framework you can use to make 2D games in Lua. It's free, open-source, and works on Windows, Mac OS X, Linux, Android and iOS.

- No need to download/install anything but for a single executable for your desired OS. Create a gamedev folder and inside it, it must have 2 important things, the love2d executable you just downloaded and your game folder with a main.lua and your assets folder inside it. Once you write your first script and want to test it out, just drag your game folder to love2d executable and it will open... simple as that!
- No need even for an IDE, cause it has a sorta built-in debugger. You can program in a simple text app and if anything goes wrong, love will try to hel you showing what's going on with your code and where you should look.
- There are executables to download for Android and iOS also, so you can make your game in your desired mobile device, cause as stated above, love has its own built-in debugger and you need is just a simple text app to code.
- It's written in LUA, a very simple and easy to understand programming language. All from movement to animation, you can make it work easier than in other framework/engines.
- It has support for Steamworks (PC), Google Play (Android) and Game Center (iOS).

External libraries:
Love Web Player (Web):  https://github.com/ghoulsblade/love-webplayer
Love-FTW (UWP): https://github.com/ahrnbom/l-veftw
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Armory3D - https://armory3d.org/ (Haxe)
Armory is an open-source 3D engine focused on portability, minimal footprint and performance. The renderer is fully scriptable with deferred and forward paths supported out of the box. Armory provides a full Blender integration add-on, turning it into a complete game development tool. The result is a unified workflow from start to finish. It supports Windows, Linux, Mac, Android, iOS, Xbox, PS4 and Nintendo Switch.

(W.I.P.)
- For a 3D engine, it's fairly simple to install inside Blender.
- It has a visual programming system.

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Kha (2D/3D)- http://kha.tech/ (Haxe)

Kha is an ultra-portable, high performance, open-source multimedia framework. It supports Windows, Linux, Mac, iOS, Android, Xbox, PS4 and Nintendo Switch.

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SDL2 (2D)- https://www.libsdl.org/ (C/C++)
Simple DirectMedia Layer is a cross-platform development library designed to provide low level access to audio, keyboard, mouse, joystick, and graphics hardware via OpenGL and Direct3D. It officially supports Windows, Mac OS X, Linux, iOS, and Android. (Also Nintendo Switch and Xbox One UWP).

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Moonworks (C#): https://gitea.moonside.games/MoonsideGames/MoonWorks

MoonWorks is a free cross-platform game development framework. Its implementation is heavily inspired by FNA, which is itself a free implementation of the Microsoft XNA API.

MoonWorks wraps native-code implementations in managed C# for clean high-level abstractions that still run fast. It's simple and it tries to stay out of your way as much as possible.

MoonWorks does provide the components you need to implement a functioning game: window management, input, graphics, 3D math utilities, and audio.

MoonWorks does not include things like a built-in physics engine, a GUI editor, or a standard rendering pipeline. These decisions and tools are better made per-team or per-project. In short, if you don't mind learning what a vertex buffer is, this framework is for you.

MoonWorks uses strictly Free Open Source Software. It will never have any kind of dependency on proprietary products.

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Flora (C#): https://github.com/sinusinu/Flora

Flora aims to be a minimal, just-enough framework that does the dirty works for you - so you can focus on building core elements of the game.

It is heavily influenced by libGDX, and took a lot of concepts from it.

Flora is designed to run on Windows. Since it is built on .NET 6 and SDL2, it could theoretically be cross-platform, but currently only Windows is considered as a supported platform. With some modification, it may run on Linux or macOS, but those platforms are not officially supported for now.

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Raylib (2D)- https://www.raylib.com/ (C)
Raylib is a programming library to enjoy videogames programming; no fancy interface, no visual helpers, no auto-debugging... just coding in the most pure spartan-programmers way.

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RetroGB (C): https://bitbucket.org/HellSuffering/retr0-gb/src/master/
A game engine using C and GBDK to make Gameboy game development a lot easier with a ready to use architecture.

• Code your game in C
• Manage sprites and/or box collision separately but in the same structure thanks to Movables (all non-static element as sprites, collision or both)
• Let your movables move freely pixel by pixel or constrain them on tiles (like RPG games) and let them interpolating their position themselves to next tile
• A complete collision system
  • Movable vs Movable blocking collision
  • Movable vs Movable overlap with automatic callback calls to manage easily what to do when movable A overlap movable B
  • Movable vs Map
  • Collision layers and layer masks to define which movable can collide with which other movable
• Sprite animations
• Animated tiles (animation for map background)
• Map loader to load map easily
• Calls to custom callbacks on map loaded and on update (called every frame) for each map
• Easy to use map scrolling, define which movable can scroll with the map and which movable can ask scrolling from its own movement
• Basic dialog system
• Music player (gbt-player implementation)
• Custom types as math 2D vectors or box
• Helper modules as functions to convert a screen position to tile position
  
  More:
  SFML(C++),
  Delver game engine(Java), Korok game engine(Go), Butano (GBA), Trial Game Engine(Common Lisp), Aether3D Game Engine(C++), is-Engine, RadixEngine, ZillaLib, Rice2D(Haxe),