Open Source Software for Self-Hosted
XAMPP
XAMPP is a free and open-source Apache web server stack used in web development. The XAMPP stack contains pre-configured versions of Apache HTTP Server, MariaDB, PHP, and Perl. XAMPP makes it really easy to install and use the stack on macOS, Linux or Windows.
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.
Gogs
Gogs is a painless self-hosted Git service that can be used to manage development projects. The lightweight footprint og Gogs allow you to host the software on the inexpensive Raspberry Pi.
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.
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.
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.
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
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.