BRUTAL Game Framework Released as Open Source, Free for Commercial Use

Ahwoo and RocketWerkz announced the open-source release of BRUTAL on 15 oktober 2026, making the C# game development framework behind Kitten Space Agency and RimWorld’s Waylith engine free to use, modify and distribute, including in commercial games, with no royalties or share of game revenue.

BRUTAL can be used to build a game directly or as the foundation for a studio’s own engine. The release gives teams an alternative to depending on a third-party engine, with access to the code they need to understand, modify and maintain their technology, the companies said in the announcement, which was datelined Auckland, New Zealand.

Six Projects Across Three Studios

The companies said the framework currently powers six game projects across three studios, and that RocketWerkz’s Kitten Space Agency won Most Innovative Hi-Tech Creative Technology Solution at the 2026 NZ Hi-Tech Awards, where judges praised the game’s simulation and graphics technology. RocketWerkz is also using BRUTAL for Art of the Rail and Torpedia, both in development.

Ludeon Studios used BRUTAL to build Waylith, its new in-house engine for RimWorld, helping extract the last parts of Unity from the game. In its announcement of Waylith and update 1.7 on 12 oktober 2026, Ludeon said the update moves RimWorld from Unity to Waylith and reported performance improvements of two to four times in its tests. The studio said a stress-tested late-game colony ran 2.2 times better on 1.7 than on 1.6, and that a modpack with 1500 mods went from 14 minutes to 6 minutes to load, while noting that individual results may vary by PC and installed mods.

Update 1.7 is available on RimWorld’s unstable Steam beta branch, while the main branch remains on version 1.6. Ludeon said 1.6 savegames load on 1.7, that 1.7 saves work when returning to 1.6, and that the vast majority of mods work without any changes. The studio said RimWorld is not the only game running on Waylith and that it is working on something new, and it thanked RocketWerkz, saying the BRUTAL framework helped make Waylith possible.

The framework’s GitHub repository lists RimWorld, Kitten Space Agency, Torpedia, Art of the Rail and Afterskies by Floating Origin Interactive as projects using BRUTAL.

Kerbal Space Program creator Felipe Falanghe collaborates with RocketWerkz on Kitten Space Agency and is using BRUTAL for his next game. Falanghe said that moving from Unity to BRUTAL was initially daunting, but that it leaves him in full control of what he has built, with complete knowledge of how those systems operate.

A Foundation, Not an Engine

At BRUTAL’s core is a custom interop layer connecting modern C# and.NET to native APIs and high-performance C/C++ libraries, including Vulkan. Supporting libraries cover mathematics, memory management, job scheduling, logging and localisation, with a focus on reducing allocations and unnecessary overhead.

The repository organizes each top-level folder as one library published as a NuGet package, so developers can reference only the ones they need. The documented inventory includes non-allocating collections and string handling, unmanaged memory and allocators, a job system and threading, vector and matrix maths types, Vulkan and OpenGL bindings, shader compilation, windowing and input through GLFW and SDL, Dear ImGui and ImPlot bindings, texture and glTF loading, FMOD and OpenAL audio, RakNet networking, and Jolt and Box2D physics.

BRUTAL’s development addressed challenges including the precision and scale required by Kitten Space Agency, a spaceflight simulation that tracks spacecraft accurately across vast distances. Meeting those demands required precise control over how positions are calculated and objects are rendered. The framework grew from a small collection of libraries over four years, with a deliberate focus on low-level functionality rather than the features of a general-purpose engine: there is no editor, no scene graph and no renderer, none are planned, and the maintainers state that pull requests drifting from a clear purpose will be rejected.

“I’m not suggesting everyone should make their own game engine. I’m suggesting every developer should have the option to do so, without having to spend four years building the foundations first,” said Dean Hall, founder and CEO of Ahwoo and RocketWerkz. “You are only as independent as your tools are.”

In mei 2025, Hall disputed a Unity notice threatening to revoke RocketWerkz’s licences, saying its evidence included two people who had never worked there, according to the announcement, which said Hall told PC Gamer the dispute validated the studio’s existing move away from Unity for new projects.

The announcement describes BRUTAL as intended for experienced programmers who want to make their own architectural decisions and are prepared to build and maintain the systems their games require, a responsibility reflected in the framework’s name.

“We called it BRUTAL because it can be brutal to use at times, and we wanted to be upfront about that,” said Rian Drake, BRUTAL’s head of engineering at Ahwoo. “There are no guardrails.”

Licence Terms and Availability

The BRUTAL licence is based on MIT with an added attribution requirement. A game or product built with the framework includes the BRUTAL copyright notice in its credits screen or equivalent, shows the BRUTAL logo before gameplay starts, and ships a NOTICE.txt file alongside the product. The logo requirement is waived for non-profit projects and where displaying it would be detrimental to the application’s purpose, and a separate commercial licence can be arranged.

The maintainers state that the licence is not yet approved by the Open Source Initiative because it has not been submitted, and that they intend to submit it and develop it with community feedback. BRUTAL was made by the RocketWerkz Enterprise team and other contributors, and is copyright 2024 Ahwoo Limited.

Prerequisites listed in the repository are the.NET 10 SDK, a Vulkan 1.3-capable GPU with current drivers for rendering, and Windows or Linux. Project files, a solution and build scripts are still to come; until then, the maintainers direct developers to the published NuGet packages and to the repository to read and fork the code.