Open source. Open possibilities.

MahApps.Metro is a UI toolkit for WPF that restyles standard controls with a modern Metro look, adds window chrome, theming, dialogs, and navigation controls without requiring control replacement.

Catppuccin is a community-driven pastel color theme offering four warm flavors with 26 colors each, plus documentation, style guide, and cross-tool integrations.

Open-source community-driven framework for managing zsh configuration with 300+ optional plugins, 140+ themes, auto-update tool, and easy installation via curl/wget/fetch.

GitHub Dark is a userstyle project that applies a dark theme to GitHub, reducing eye strain during coding sessions. It includes syntax highlighting themes for GitHub, CodeMirror, and Jupyter, and is designed to be used with browser extensions like Stylus.

A documentation framework built on MkDocs: write in Markdown and produce a searchable, customizable static site in minutes, with responsive layouts, 60+ languages and MIT licensing.

WPF UI is an open-source library that brings Microsoft's Fluent Design System to Windows Presentation Foundation applications, offering themed styles, modern controls like Navigation, NumberBox, Dialog, and Snackbar, plus Visual Studio integration and NuGet distribution.

Fyne is a cross-platform GUI toolkit written in Go, inspired by Material Design, enabling desktop and mobile apps from a single codebase with easy-to-use APIs and packaging tools.

Morphous is a static TanStack Start catalog of nature-inspired design systems. It publishes motif assets, light and dark design-system boards, recorded prompts, and shadcn/tweakcn-compatible theme exports, with catalog validation, preview generation, tests, and GitHub Pages deployment.

Marigold is a React implementation of the Marigold Design System, built on react-aria and Tailwind CSS. The monorepo ships component and theme packages, a Storybook workspace, a Next.js documentation site, Vitest tests and CI-driven releases via Changesets.

Nebular is a customizable Angular UI library based on the Eva Design System, offering 4 visual themes, 35+ Angular UI components, a theming engine with runtime theme switching and CSS custom properties mode, plus Eva Icons SVG support and configurable authentication strategies.