Godot Engine – Multi-platform 2D and 3D game engine

Open Source Computer Vision Library

KeePassXC is a cross-platform community-driven port of the Windows application “Keepass Password Safe”.

Self-hosted game stream host for Moonlight.

Cross-platform, graphics API agnostic, "Bring Your Own Engine/Framework" style rendering library.

Simple and Fast Multimedia Library

ArrayFire: a general purpose GPU library.

Lightweight C++ command line option parser

Mapnik is an open source toolkit for developing mapping applications

Arduino library for controlling single-wire LED pixels (NeoPixel, WS2812, etc.)

Human-friendly unit testing for C++11

A header only C++11 library for parsing TOML