MAME is a multi-purpose emulation framework
JUCE is an open-source cross-platform C++ application framework
Web Framework built on top of Qt, using the approach of Catalyst
Scripting platform, modding framework and VR support for RE Engine
A modern, C++-native, test framework for unit-tests, TDD and BDD
Cross platform toolkit for creative coding in C++
A flight software and embedded systems framework
NativeScript for Android using v8
A lightweight game server framework implemented with Actor Model
A framework for building native Windows apps with React
Open source framework simplifying the creation of C++ applications
MNN is a blazing fast, lightweight deep learning framework
Light and powerful C++ web framework for web applications
Static reflection for enums (to string, from string, iteration)
Fastest feature-rich C++11/14/17/20 single-header testing framework
TreeFrog Framework, High-speed C++ MVC Framework for Web Applications
Industrial-grade RPC framework used throughout Baidu
Cross-platform layout engine which implements Flexbox
Real-Time Event Frameworks based on active objects & state machines
A cross-platform GUI library
Original source code of Ultimate Toolbox, TCP/IP and Grid for MFC
Borland's Object Windows Library for the modern age
Support for legacy OpenGL in core profiles
ALFOUR Programming language. Simple, safe, power, multi-platform.
Source code is here - https://sourceforge.net/projects/lcmd-git/