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Open-source clones of classic games on GitHub, and what each one still needs from you
OpenTTD, OpenRA, Mindustry and Cataclysm-DDA are four of the most-starred game projects on GitHub. Three are engine reimplementations that need something from you. Here is the licence and the catch for each.
- Topic
- Open source
- Difficulty
- beginner
- Spoilers
- None
There is a specific genre of GitHub project that gets recommended constantly and understood rarely: the open-source reimplementation of a commercial game. The pattern is almost always the same. Someone rebuilds the engine from scratch, publishes the source, and the game data stays with the original publisher. That distinction decides whether you can just download and play.
Four of the biggest examples, with the licence and the catch stated up front.
OpenTTD — a business simulation with a 30-year lifespan
OpenTTD is an open-source simulation based on Transport Tycoon Deluxe, the 1994 Chris Sawyer game where you build a transport empire across a procedurally generated map.
- Licence: GPL-2.0, shipped as
COPYING.mdat the repository root — which is why GitHub reports the licence as “Other” rather than detecting it - Stars: ~8,300
- Language: C++
The catch, and the good news: unlike most projects in this category, OpenTTD is fully playable without owning anything. It bundles free replacement graphics, sound and music, so a fresh download is a complete game. If you do own Transport Tycoon Deluxe, you can point it at those files instead and get the original art.
OpenTTD is also the most approachable thing on this list. There is no combat, no fail state, and no time pressure — which makes it an unusually good first open-source game to install if you are curious about the category.
OpenRA — Command & Conquer, rebuilt as an engine
OpenRA is a real-time strategy engine for the early Westwood games, written in C# with SDL and OpenGL. It covers Command & Conquer: Tiberian Dawn, Red Alert and Dune 2000.
- Licence: GPL-3.0
- Stars: ~17,400 — the most-starred project here
- Runs on: Windows, Linux, BSD and macOS
The catch: OpenRA ships the engine and the game logic, not the original assets. For the full games you supply your own copy of the Westwood data files. It also modernises as it goes — unit behaviour, balance and interface are the project’s own interpretation rather than a faithful reproduction, which is either the appeal or the deal-breaker depending on what you wanted.
Mindustry — the one that is genuinely free and complete
Mindustry is a tower-defence and factory-building game where you mine, route resources across conveyor networks, and defend a core against waves.
- Licence: GPL-3.0
- Language: Java
- Platforms: desktop and mobile, free from the project
The catch: there is not one. Mindustry is a complete, original game released as open source, not a reimplementation of somebody else’s. You download it and play the whole thing. The desktop and Android builds are free, and there is a paid Steam version that exists to support the developer rather than to unlock anything.
If you only install one thing from this article, install this. It is also the one that will quietly eat forty hours.
Cataclysm: Dark Days Ahead — the deepest survival game on GitHub
Cataclysm-DDA is a turn-based survival game set in a post-apocalyptic world, built by over a thousand volunteers. It is turn-based, tile-based, and almost absurdly detailed — vehicle construction, crafting trees, mutation systems, and a world that generates its own history.
- Licence: Creative Commons Attribution-ShareAlike 3.0 — for the code, which is unusual and worth noticing
- Stars: ~13,200
- Language: C++
The catch: the licence. CC BY-SA is a content licence, not a software one, and using it for source code is an unconventional choice that has been discussed in the project for years. For a player it changes nothing. For anyone planning to reuse the code, read it carefully — ShareAlike is a copyleft condition, and the “Attribution” part applies to a body of work maintained by more than a thousand people.
The other catch is the interface. It is a traditional roguelike with a keyboard-driven menu system, and the learning curve is a cliff. The payoff is a simulation with more depth than anything commercial in the genre.
The pattern worth remembering
| Project | Licence | Do you need to own anything? |
|---|---|---|
| OpenTTD | GPL-2.0 | No — free assets are bundled |
| OpenRA | GPL-3.0 | Yes, for the full campaigns |
| Mindustry | GPL-3.0 | No — complete original game |
| Cataclysm-DDA | CC BY-SA 3.0 | No — complete original game |
The distinction that matters is not how famous the project is. It is whether it is a reimplementation or an original work. Reimplementations inherit a dependency on assets they cannot legally ship. Originals do not.
When you find a new project in this space, that is the first question to ask — and the licence file is the second.