Indie Tooling

BRUTAL is free. Read the licence before you build on it

The C# framework under RimWorld's new engine is free for commercial games. It has no editor or renderer, and its licence asks for more credit than MIT.

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5 min read

A stack of coloured blocks labelled Vulkan, SDL, ImGui, FMOD, Jolt and RakNet on a C# base, with an empty dashed slot marked editor on top. Beside it, a licence file with three ticked conditions: credits screen, NOTICE.txt and logo splash, plus a tag reading $0.
Illustration: Indie Tooling

BRUTAL, the C# framework underneath Ludeon’s new Waylith engine for RimWorld, is now free to download and use in commercial games. Dean Hall’s companies Ahwoo and RocketWerkz released it on 15 October, three days after Ludeon announced RimWorld’s move off Unity. There are no royalties. There’s also no editor, no scene graph and no renderer, and the licence asks for more credit than the MIT licence it’s based on.

What BRUTAL is

BRUTAL is a set of low-level libraries for building a game, or your own engine, in modern C#. Its README lists the .NET 10 SDK as a requirement, plus a Vulkan 1.3 GPU if you render. At its core is an interop layer that lets C# code call native C and C++ libraries directly. Around that sit libraries for maths, memory, strings, collections, job scheduling, logging and localisation. It uses unmanaged memory and unsafe code where it helps, to avoid allocations and garbage collection overhead.

On top of that are bindings for libraries many developers already know:

  • Graphics: Vulkan and OpenGL, plus shader compilation.
  • Windows and input: GLFW and SDL.
  • Tools UI: Dear ImGui and ImPlot.
  • Assets: glTF loading and texture formats.
  • Audio: FMOD and OpenAL.
  • Networking: RakNet.
  • Physics: Jolt and Box2D.

Each top-level folder ships as its own NuGet package, so you take only what you need. What you don’t get is anything that decides how your game is structured. The README says there’s no editor, no scene graph and no renderer, and the team isn’t adding them. You write your own renderer on the Vulkan bindings. Hall compares BRUTAL to the Linux kernel, and a finished engine to something like Ubuntu.

The team, led by Ahwoo’s head of engineering Rian Drake, is open about who it’s for. Drake says there are “no guardrails”, and the framework doesn’t try to be simple. It’s aimed at experienced programmers.

Who’s using it

Ahwoo says six projects across three studios use BRUTAL, and the README names five of them. RocketWerkz builds Kitten Space Agency directly on it, along with two games in development, Art of the Rail and Torpedia. Kerbal Space Program creator Felipe Falanghe is using it for his next game, according to Ahwoo. The README also lists Afterskies, from Floating Origin Interactive.

The best-known result is RimWorld. Ludeon’s announcement credits RocketWerkz, whose framework it says helped make Waylith possible. In Ludeon’s own tests, a late-game stress-test colony ran 2.2 times faster on update 1.7 than on 1.6, and a 1,500-mod pack loaded in 6 minutes instead of 14. Ludeon says results vary by PC and mod list. Update 1.7 is still on Steam’s unstable beta branch.

The licence, and the catch in it

The basics are simple. You can use BRUTAL in commercial games, there are no royalties and no revenue share, and the licence has no revenue cap. You can fork it and build your own engine on it, which Hall encourages.

The licence is custom. GameFromScratch calls it a modified MIT licence with an attribution requirement. Any game built with BRUTAL must:

  • Put BRUTAL’s copyright notice in its credits screen, or equivalent.
  • Ship the NOTICE.txt file alongside the game.
  • Show the BRUTAL logo before gameplay starts, unaltered except for scaling, legible, and no less prominent than other companies’ logos.

The licence text itself lets you skip the logo only with written permission from Ahwoo, or if your product can’t display graphics. The README adds that Ahwoo waives the logo for non-profit projects and where it would harm the app’s purpose. If you don’t want to meet these terms, Ahwoo offers a separate commercial licence.

The licence isn’t approved by the Open Source Initiative (OSI). The README says Ahwoo hasn’t submitted it yet but plans to, and to refine it with community feedback. In the announcement thread, one forum user has already questioned whether a non-OSI licence should be called open source, rather than source-available.

Hall’s reason for the extra attribution is AI. GameFromScratch quotes him on Reddit saying credit is harder to preserve as AI and agents write more code, and that credit is what matters most to him.

A splash screen is a small ask next to Unreal’s 5% royalty on lifetime gross revenue above US$1 million. It’s still a condition you’ll need to plan for, so read the licence file yourself before you commit a project to it.

Why Hall gave it away

Hall has argued for frameworks over engines for a while. In a November 2025 interview with Game Developer, he said engines lead developers into scene-based thinking, while a framework makes you decide what your game needs first. He also said RocketWerkz found it easier to recruit programmers for its framework than for Unreal.

At launch, he said you’re “only as independent as your tools are”. The announcement points to a May 2025 notice from Unity threatening RocketWerkz’s licences, which Hall disputed. Both Hall and Drake added caveats. Hall says he isn’t suggesting everyone should build their own engine, and Drake says BRUTAL isn’t the tool everyone should use.

Rough edges at launch

BRUTAL has been in development since 2022, but the public release is early. The README says project files, a solution and build scripts are still to come, so for now you use the NuGet packages. On launch day, a user on Ahwoo’s forum reported the documentation site wasn’t public yet. The README lists Windows and Linux. Drake said in December 2025 that Apple Silicon Macs were supported too, but the current requirements don’t mention macOS. Nothing has been said about consoles or mobile.

Should you care?

You are Our verdict
Shipping your first game in Godot, Unity or GameMaker No. BRUTAL gives you building blocks, not a game engine. Finish your game.
An experienced C# programmer who wants your own engine Yes. Spend a weekend on a prototype, and read the licence before you go further.
Making a simulation or management game with heavy modding Worth a look. It’s the stack behind RimWorld’s speed-up, and plain .NET code is friendly to modders.
Targeting consoles or mobile Not yet. Neither has been mentioned.

Sources

Topicsbrutalahwoorocketwerkzc#frameworkslicencesrimworld

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