This list is woefully out of date. I need to take a pass through it, but honestly I am not sure it's possible to have one that is really up to date and relevant any more.
You underestimate the shelf-life of a lot of this stuff. If you'd like a quick modernization jump, fixing the broken Doxygen link and adding these would go a long way to that:
Godot
Download:
https://godotengine.org/
Platform: Windows/Linux/OS X/lots
Category: IDE's, Compilers, and Editors
Description: Godot is a game engine and IDE, programmable in C# or its own Python-like language and extensible with .dll/.so/.dylib files, which is also gaining popularity as a way to make tools for assisting in game creation.
Rust
Download:
https://www.rust-lang.org/tools/install
More data:
https://www.hobofan.com/rust-interop/
Platform: Windows/Linux/OS X/lots
Category: IDE's, Compilers, and Editors
Description: Rust is a memory-safe, un-managed programming language focused on compile-time correctness, with a broad ecosystem of bindings/generators for writing compiled extensions for other languages.
Sphinx
Download:
https://www.sphinx-doc.org/en/master/usage/installation.html
More data:
https://www.sphinx-doc.org/en/master/index.html
Category: Teaming and Communications
Description: Sphinx is a language-agnostic documentation system using reStructuredText with support for exporting to many formats and a plugin for extracting API documentation from Python code.
mdBook
Download:
https://github.com/rust-lang/mdBook/releases
More data:
https://rust-lang.github.io/mdBook/
Category: Teaming and Communications
Description: mdBook is a language-agnostic documentation system using Markdown which is the
de facto standard for writing non-apidoc documentation in the Rust ecosystem.
Django
Platform: Windows/Linux/OS X
Download:
https://www.djangoproject.com/download/
More data:
https://djangopackages.org/
Category: Web Development
Description: Python's counterpart to Ruby on Rails, with a giant ecosystem of reusable components.
gdbgui
Platform: Linux/OS X
Download:
https://www.gdbgui.com/installation/
More data:
https://www.gdbgui.com/
Category: Debugging and Forensic Tools
Description: An advanced open-source browser-based GUI for the gdb debugger
x64dbg
Platform: Windows
Download:
https://sourceforge.net/projects/x64dbg/files/snapshots/
More data:
https://x64dbg.com/
Category: Debugging and Forensic Tools
Description: An open-source debugger GUI for Windows
Blender
Platform: Windows/Linux/OS X
Download:
https://www.blender.org/download/
More Info:
https://www.blender.org/features/
Category: Content Tools
Description: An open-source 3D modelling tool which can also be used as a non-linear video editor
FontForge
Platform: Windows/Linux/OS X
Download:
https://fontforge.org/en-US/downloads/
More Info:
http://designwithfontforge.com/en-US/index.html
Category: Content Tools
Description: THE open-source font creator/editor
Inkscape
Platform: Windows/Linux/OS X
Download:
https://inkscape.org/release/
More Info:
https://inkscape.org/about/
Category: Content Tools
Description: An open-source vector graphics editor with native SVG capabilities
Krita
Platform: Windows/Linux/OS X
Download:
https://krita.org/en/download/
More Info:
https://krita.org/en/features/
Category: Content Tools
Description: Open-source digital painting tool
LMMS
Platform: Windows/Linux/OS X
Download:
https://lmms.io/download
More Info:
https://docs.lmms.io/user-manual
Category: Content Tools
Description: Open-source music-creation studio
SDL
Platform: Windows/Linux/OSX/etc.
Download:
https://github.com/libsdl-org/SDL/releases/latest
More Info:
https://www.libsdl.org/languages.php
Category: Toolkits and Frameworks
Description: The open-source platform abstraction layer Valve supports and funds for writing game engines that easily port to anything and automatically integrate with Steam's gamepad configurator.