An original, community-driven open-world game project, built on Unreal Engine 5. The quality bar is the fidelity of modern AAA open-world games: a dense, living coastal city with seamless streaming, vehicles, crowds, water, and weather.

⚠️ This is an original, unaffiliated project. It is not associated with, endorsed by, or connected to Rockstar Games or Take-Two Interactive, and it contains no assets, code, trademarks, or content from any commercial game. Any "AAA open-world" comparison describes a quality benchmark, nothing more.

• Game code (everything in Source/, build scripts, and configuration) is licensed under the MIT License.
• Game assets we author (our own files under Content/, excluding the Content/GTCaliberAssets/ submodule) are licensed under CC BY 4.0, with provenance tracked in docs/ASSETS.md. The third-party assets in the Content/GTCaliberAssets/ submodule are separately licensed and NOT CC BY 4.0 (see docs/ASSET_HANDLING.md and the "Assets" section below).

This is not "fully open-source software," and cannot be. The project runs on Unreal Engine 5, which is proprietary: Unreal is provided by Epic Games under the Unreal Engine EULA (source-available, royalty-bearing, not an OSI/FSF open-source license). You must obtain the engine yourself from Epic; it is not redistributed here, and the engine cannot be relicensed under MIT. What is open here is our own game code (MIT) and our own art (CC BY 4.0), sitting on top of a proprietary engine. Any Epic sample content, Fab marketplace assets, or engine plugins added later remain under their own Epic/third-party terms and are likewise not open source.

In short: MIT-licensed game code and CC-BY assets, on a proprietary engine.

🛠️ In active development; not yet a playable build. The project is a ground-up Unreal Engine 5.7 (C++) port of a prior prototype. The work is staged:

• Wave 1, tested logic core (complete): pure gameplay/AI/economy models (scoring, ballistics, NPC decision cores, faction/territory, economy, missions, weapons, vehicle logic, and more) ported to C++ with automation-test parity.
• Wave 2, subsystems (complete): self-wiring managers landed as UE GameInstance/World Subsystems across four batches (progression, player stats, save/persistence, wanted/arrest, NPC dialogue, disguise, roster, mission coordinators, and more).
• Wave 3, engine/feel (in progress): the C++ framework is merged (player pawn, context interaction, HUD base, Enhanced Input, armor reconciliation as tested logic); rendering, World Partition streaming, Chaos vehicles, Mass AI crowds/traffic, animation, audio, and UMG follow.

The logic core currently passes a full headless automation suite of 1246 tests.

UE 5.7, macOS (Apple Silicon verified) / Windows. You provide the engine; the repo provides the game.

# 1. Install Unreal Engine 5.7 from the Epic Games Launcher (accept the UE EULA).
# 2. Install Git LFS once per machine:
git lfs install
# 3. Clone WITH submodules (the game art lives in a submodule; see "Assets" below):
git clone --recurse-submodules <repo-url>
#    (already cloned without it? run: git submodule update --init --recursive)
# 4. Pull the Git LFS asset objects for the submodule:
cd Content/GTCaliberAssets && git lfs pull && cd -
# 5. Generate project files and build the editor target
#    (right-click the .uproject, "Generate project files", or use the engine's
#     Build.sh / UnrealBuildTool for GTC_UE5Editor).

Headless tests run via the engine's Automation system against the GTC.* test prefixes. See Source/ for the module layout and the in-module tests under each system's Tests/ folder.

Most game art is not in this repository. It lives in a private Git LFS submodule mounted at Content/GTCaliberAssets/ (about 15 GB), sourced from:

• Fab / PropHaus (Standard License) for the city/environment set,
• Epic Games (Unreal Engine EULA) for the Mannequin and template content,
• Cesium for Unreal for geospatial config.

These are separately licensed and are NOT CC BY 4.0; their handling rules and per-set provenance live in docs/ASSET_HANDLING.md. This repository tracks only a submodule pointer, never the asset files.

Access is gated. Fetching the assets requires read access to the private asset repository. Without it you can clone and build the code, but you will not get the art, and the project is not runnable as-is. This is intentional: licensed and paid assets are never redistributed here. Contributors who need the art should request access; the code stays open regardless.

Contributions are welcome: programmers, 3D artists, audio, writers, playtesters.

1. Read CONTRIBUTING.md.
2. Pick an open task.
3. Open a PR. CI validates headlessly; the build + automation tests must pass.

By contributing code you agree to license it under MIT; by contributing assets you agree to CC BY 4.0 and attest you hold the rights (see docs/ASSETS.md). AI-generated assets are accepted only when the generator's terms permit CC BY 4.0 redistribution and that is recorded in the provenance ledger.