Open Source Software for Self-Hosted
Koa
Koa is a free and open-source, expressive HTTP middleware framework for Node.js. Koa provides a great developer experience that makes writing web applications and APIs more enjoyable. Koa's middleware stack flows in a stack-like manner, allowing you to perform actions downstream then filter and manipulate the response upstream. Only methods that are common to nearly all HTTP servers are integrated directly into Koa's small codebase. This includes things like content negotiation, normalization of node inconsistencies, redirection, and a few others.
PostGraphile
PostGraphile (previously known as PostGraphQL) is a free an open-source software project that lets you spin up GraphQL APIs on top of an existing PostgreSQL database, instantly. PostGraphile automatically detects tables, columns, indexes, relationships, views, types, functions and comments in your database. Based on that information it generates a GraphQL server and API which is automatically updated when changes are made to the database or its data.
Simple Machines Forum
Simple Machines Forum or SMF in short is a free and open-source forum software. SMF can be used to build your own online community that you self-host on a host of your choice. Simple Machines Forum comes packed with features for customization, extension and management of your community. The template engine puts you in control of the design of your community. The plugin architecture makes it easy to extend and provide further feautres though third-party built packages.
Foundation
Foundation is a free and open-source HTML & CSS framework that can be used to build and design websites and web applicaitons in a structured way.
Hexo
A fast, simple & powerful blog framework and static site generator powered by Node.js. With Hexo, you can quicly build static websites and blogs that generates at an increaible speed. Hexo generates hundreds of files per seconds and quickly builds and push your website to deployment, with a single command. You can have your site up and running in minutes on well known hosts and platforms like GitHub Pages, Heroku, Digital Ocean and other platforms. The framework support all features of GitHub Flavored Markdown and most Octopress plugins by default. Hexo is released free and open-source under the MIT License.
OpenUserCSS
With OpenUserCSS you can change the look of other websites. OpenUserCSS contains a wide range of themes that are easy to apply, to make websites more readable.
Filestash
Filestash is a free and open-source Dropbox-like file manager that can be used to manage data anywhere. Filestash allows you to bring your own backend or create your own by implementing a simple interface. Currently, Filestash works with Amazon S3, SFTP, FTP, FTPS, Minio, Backblaze, GIT, Github, Gitlab, WebDav, LDAP, CalDAV, CardDAV, Mysql, Dropbox, Google, Drive Gogs Gitea. Through Filestash intuitive interface you can manage photos and files and easily share then with friends and family via regular links or social accounts.
HTTPie
HTTPie is a command-line HTTP client that makes it easy to interact and work with RESTful APIs. The CLI provided by HTTPie is designed to be as human-friendly as possible and is loved by developers creating services for the web. HTTPie can be used for testing, debugging, and generally interacting with any API and HTTP server.
Gatsby
Gatsby is a free and open source framework and site generator that helps developers to build blazing fast websites and apps. The framework is based on React and include a plugin ecosystem that can be used to extend the capabilities of Gatsby. With Gatsby you can pull data from headless CMSs, SaaS services, APIs, databases, even your file system with the help of GraphQL. If you are looking to build a fast website that scales with time, Gatsby might your best pick.
UIkit
UIkit A lightweight and modular front-end framework for developing fast and powerful web interfaces.