JUCE is an open-source cross-platform C++ application framework
Plugin driven WYSIWYG markdown editor framework
Completely customizable framework for building rich text editors
Math Parser: Java, C#, C++, Kotlin, Android, and all .NET platforms
Espressif IoT Development Framework
Lexical is an extensible text editor framework
A cross-platform framework using Vue.js
A web-based IDE for HTML5 game development. Powered by Phaser
Vanilla JavaScript image gallery & lightbox
Dark powered asynchronous completion framework for neovim/Vim8
Unity Node Editor: Lets you view and edit node graphs inside Unity
Midje provides a migration path from clojure.test