Free Software for Self-Hosted
AlaSQL
AlaSQL is a free and open-source lightweight client-side in-memory SQL database designed to work in browser and Node.js. The database is written in JavaScript and does not use the browsers WebSQL database. The AlaSQL server is fully functional and supports JOINs, GROUPs, UNIONs, ANY, ALL, IN, subqueries and very limited transactions support.
Wiki.js
With Wiki.js you can run a blazing fast Wiki built with performance in mind. Wiki.js is an extensible, free and open source Wiki software written in JavaScript. Wiki.js brings a modern approach to documentation and Wiki writing, it provides a simple to use WYSIWYG editor, a Markdown editor and a visual builder to please all types of workflows. All content moderation is also tracked on a Wiki.js-powered site, which means that you can an revert to a previous state or recover a deleted page at any time and get a broad overview of content evolution. Allowing you to visually compare two versions of the same page to see exactly what changed. Wiki.js runs on virtually any platform and is compatible with either PostgreSQL, MySQL, MariaDB, MS SQL Server or SQLite.
Rome
Rome is a free and open-source JavaScript build tool that has strong conventions and aims to have minimal configuration. The toolset includes a linter, compiler and bundler for JavaScript, TypeScript, JSON, HTML, Markdown, and CSS. Rome has zero dependencies, and has largely been written from scratch by people from Facebook.
Webpack
Webpack is an open-source module bundler for JavaScript. Its main purpose is to bundle JavaScript files for usage in a browser, yet it is also capable of transforming, bundling, or packaging just about any resource or asset. It can transform front-end assets like HTML, CSS, and images where corresponding loaders ar included and takes modules with dependencies and generates static assets representing those modules.
Flutter
Flutter is an open-source UI software development kit created by Google. Flutter allows developers to write Android and iOS application in Dart. Flutter can be installed on any desktop computer and server that runs Linux, macOS or Windows. The SDK provide developers with a great developer experience with hot reload, that allows for quick iterations and a quick development workflow when building UI's, adding features and fixing bugs.
Docusaurus
Docusaurus makes it easy to maintain open source documentation websites. With Docusaurus you can wriet docummentation and blog posts using Markdown and save time when doing so. Docusaurs automatically publish your files as static html files ready to serve on the web.
MkDocs
MkDocs is a fast, simple and open-source static site generator that's geared towards building project documentation for software projects. With MkDocs it's easy to setup documentation with source files that are written in Markdown, and configured with a single YAML configuration file. When it is time to host your documentation, MkDocs builds completely static HTML sites for GitHub pages, Amazon S3 or a hosting provider of your choice.
StackEdit
StackEdit is an open-source, browser-based Markdown editor with a wide varity of features. It allows you to edit multi-Markdown documents in offline and online modes, lets you store documents in HTML and PDF formats, and collaborate with friends and co-workers though third-party cloud services such as Dropbox, GitHub and Google Drive. A bonus feature of StackEdit is the integration with blogging platforms like Blogger, Tumbler, and WordPress where your documents can be outputted as Markdown or HTML with Handlebars template engine
ProcessWire
With ProcessWire you can connect all your content seamlessly and making content management fast, easy and fun. ProcessWire is a free and open-source content management system and framework released under the Mozilla Public License 2.0. The CMS is built around an API wit similar naming connventions to that of jQuery, which makes it easier to use for JavaScript developers. It also provides a secure foundation, proven scalability and the performance needed to manage content online sucessfully.
LayerBB
LayerBB is a small yet feature rich, free and open-source community software written in PHP. LayerBB enables you to quickly and easily start your own community while providing great flexibility and customisability.