# OpenYSM is a GeckoLib player model mod with two different licences inside it

> A Minecraft mod that replaces the vanilla player model, built on GeckoLib and Bedrock Edition assets, and pitched as the fully open source alternative to Yes Steve Model. Its README opens with a retirement note rather than documentation, and the model files it bundles are not under the same terms as its source code.

**OpenYSM/OpenYSM** — Yes-Steve-Model idea ready.

- Repository: https://github.com/OpenYSM/OpenYSM
- Stars: 436 · Forks: 75
- Language: Java
- License: MIT
- Published: 2026-09-20 · Updated: 2026-09-20 · Language: en
- Canonical page: https://hysenlabs.com/projects/openysm-openysm

## The README opens with a retirement note

Before any documentation, the file leads with a section titled farewell thoughts, and it is an explanation of why the project is winding down rather than a description of how to use it.

The stated plan was to pressure the closed source Yes Steve Model project into open sourcing, through publishing work that competed with it. The note says that goal was met, that a promised contest between iterations is being abandoned, and that the authors are stepping aside because the now official open source version should gradually absorb the improvements they had been demonstrating.

Those improvements are named: user interface work, loading work, memory optimisation, and GPU rendering. The argument is that there is no point continuing to compete when the upstream has opened up, and that moving to the official ecosystem is the sensible outcome.

The closing line credits the developers by name, including TartaricAcid and 番茄布丁, for making the right decision in the end. What this tells a reader arriving cold is that the repository's purpose has largely been spent, and that the technical documentation below the farewell is the part written for users rather than for the project's own campaign.

## GeckoLib at the core, Bedrock assets underneath

The actual project description is short. OpenYSM is a Minecraft mod based on Yes Steve Model that modifies the vanilla player model, so what it replaces is the character you see when you look at yourself.

The core runs on GeckoLib, the animation library, and the model and animation files it consumes are the ones from Minecraft Bedrock Edition rather than the Java edition formats. That choice has a practical consequence for anyone making content: the input format for a custom player model or animation is the Bedrock one, which is a different authoring pipeline from the Java edition resource pack format.

The stated purpose is to be a fully open source alternative that can be freely modified and redistributed, built on top of the earlier LegacyYSM codebase rather than starting from nothing. In other words, the claim is not new features but open licensing and open tooling over an existing player model replacement.

No configuration surface is described anywhere in the visible text. Where options live, what they are called, and how the model is selected at runtime are all left to the mod's own interface or to the wider mod documentation, which is not linked from this README.

## MIT for the source, CC BY-NC-SA for one bundled model

The licensing section is the part of this README with real consequences, because it splits the repository into two different sets of terms.

The source code is MIT. You may use, change and redistribute it, keeping the original copyright notice, and the full terms are in the `LICENSE` file at the root.

The model files bundled in the repository are not under those terms. The default models are CC0, the Creative Commons Zero dedication, with no restrictions at all. The Wine Fox model is CC BY-NC-SA 4.0, which permits non-commercial use only, requires attribution, and requires derivative works to carry the same licence.

So the repository as a whole is not uniformly permissive, and a build that ships the Wine Fox model inherits non-commercial and share-alike obligations that the MIT grant does not override. If you plan to redistribute a jar with that model in it, that is the line to read twice.

The optional C++ rendering library lives in a separate repository, so it carries its own terms that this README does not restate. Three licences in one dependency chain is the situation to check before shipping.

## The build command names a different repository

The build instructions are three lines, and the first one is not the repository you are reading:

```bash
git clone https://github.com/OpenYSMDev/ModernYSM.git
cd ModernYSM
./gradlew build
```

Two mismatches sit in those three lines. The clone points at a repository named ModernYSM rather than OpenYSM, and it sits under an organisation spelled OpenYSMDev while this repository is under OpenYSM. The optional C++ library is likewise at OpenYSMDev with a lowercase name.

The tree supports the reading that the native work and the Java mod have been living in adjacent repositories rather than one. `CMakeLists.txt`, a `jni/` directory, a `libs/` directory and a `.gitmodules` file are all present at the root, and `build.gradle`, `settings.gradle`, `gradle.properties`, the `gradle/` directory and both `gradlew` and `gradlew.bat` are there too.

Because the Gradle wrapper is committed, `./gradlew build` needs no locally installed Gradle, which is the one part of the build story that is self-contained. Build output lands in `build/<platform>/libs/`, so a single build produces a platform-specific jar rather than one artefact for everything.

## An optional C++ renderer with no build instructions

The performance option is described in a single sentence: the project uses an optional C++ library for faster rendering, and that library lives at the openysm.cpp repository.

Optional is doing real work in that sentence. It means the Java and GeckoLib path is the supported baseline and the native library is an accelerant, which is a sensible way to structure a mod where the renderer is the hot loop but the rest is ordinary Java.

What the README does not give is any instruction for building or wiring it up. There is no compiler version, no platform matrix, no Gradle flag that turns it on, and no note about which Minecraft platforms it covers. The presence of `CMakeLists.txt`, `jni/` and `libs/` in this repository says the native side has a home here, but not how to activate it.

So if you want the faster renderer, the repository you must read is the other one. If you do not, nothing is lost by ignoring it, and `./gradlew build` is the whole story. That asymmetry is worth knowing before you budget time for it.

## What they claim to have rebuilt from the closed version

The farewell section contains the project's own account of its technical achievement, and it is specific about the three parts.

They say they researched the encryption in the closed source model, implemented decryption, and implemented re-rendering, then reimplemented all of the functionality found in new versions of the original mod. Decryption and re-rendering are the interesting pair: the first makes the protected model format readable at all, and the second is what turns a decoded mesh into something a live renderer can display correctly.

That work is also the reason the farewell exists. The argument runs that none of this would have been possible to open source within a few years without an outside implementation existing, which is the mechanism that made upstream open sourcing urgent rather than inevitable.

What none of it documents is the part you would want as a content author: no description of the model format, no compatibility statement against specific versions of the original mod, and no list of which animation features are supported. The tag naming hints at the answer, carrying a YSM version inside it, but the README does not spell out the relationship.

## One tagged build, dated 2026-05-06

The repository publishes a single release, and its tag packs three separate facts into one string: `ysm-2.6.5-forge+mc1.20.1`.

That is a YSM version of 2.6.5, the Forge mod loader, and Minecraft 1.20.1. Encoding all three in the tag tells you the mod targets one specific game version on one specific loader, which is the usual arrangement for Minecraft mods and also means it will not run on a newer Minecraft without a rebuild.

The tag was published on 2026-05-06. The last push was on 2026-09-27, and the repository is not archived. So there has been code movement in the four and a half months since the release with no new tag cut, which lines up with a project that says it has handed over to the official ecosystem.

For anyone building this, the practical reading is to treat that one release as a reference point rather than a dependency. The source tree is the current state, `./gradlew build` is how you produce your own artefact, and contributions of any kind are invited, from issues through documentation and bug fixes to new features.

## Conclusion

OpenYSM makes sense if you want a player model mod whose source you can read and change, and you author in Bedrock Edition asset formats. It is the wrong choice for a commercial re-release as it stands, because the Wine Fox model bundled in the repository is CC BY-NC-SA 4.0, and no commercial use is permitted on those terms, while the default models are CC0 and unrestricted. Before you build, check two things: that the clone line in the README still points where you expect, since it names a ModernYSM repository rather than this one, and that the optional C++ renderer is something you actually need, because no build instructions for it appear in the visible documentation. Also treat the single tagged build from 2026-05-06 as a sample rather than a dependency: with one release tag and a last push on 2026-09-27, building from source is the realistic path. The repository is not archived and reports the MIT licence at the top level, with the model terms documented separately below it.

## FAQ

### What is OpenYSM and what does it do in Minecraft?

It is a mod based on Yes Steve Model that modifies the vanilla player model, built on GeckoLib and using Minecraft Bedrock Edition model and animation files. It is positioned as a fully open source, freely modifiable replacement for the earlier LegacyYSM codebase.

### Can I use OpenYSM commercially?

That depends on which files you ship. The source code is MIT, and the default bundled models are CC0 with no restrictions, but the Wine Fox model is CC BY-NC-SA 4.0, which permits non-commercial use only, requires attribution, and requires derivatives to use the same licence.

### How do I build OpenYSM from source?

Clone the repository, change into the directory and run the Gradle wrapper with `./gradlew build`. The wrapper is committed so no local Gradle install is needed, and the output jar lands under `build/<platform>/libs/`. Note that the clone line in the README names a ModernYSM repository rather than OpenYSM itself.

### Does OpenYSM need a C++ library to run?

No, it is optional and described as being there for faster rendering. The library lives in a separate openysm.cpp repository, and the visible documentation gives no instructions for building or enabling it, so the Java and GeckoLib path is the supported baseline.

### Which Minecraft version and mod loader does OpenYSM target?

The single release tag reads `ysm-2.6.5-forge+mc1.20.1`, which encodes a YSM version of 2.6.5, the Forge mod loader, and Minecraft 1.20.1. It was published on 2026-05-06.

### Why did the OpenYSM authors stop developing their fork?

The README leads with a farewell note explaining that they set out to get the original mod open sourced, that it then open sourced, and that they judged their goal met and moved to the official ecosystem. The improvements they had demonstrated were user interface, loading, memory and GPU rendering work.

## Sources

- [Issues](https://github.com/OpenYSM/OpenYSM/issues)
- [License: MIT](https://github.com/OpenYSM/OpenYSM/blob/main/LICENSE)
- [OpenYSM/OpenYSM on GitHub](https://github.com/OpenYSM/OpenYSM)
- [README](https://github.com/OpenYSM/OpenYSM/blob/main/README.md)
- [Releases](https://github.com/OpenYSM/OpenYSM/releases)

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Hysen Labs editorial analysis, written from the project's own repository and release notes. Cite the canonical page: https://hysenlabs.com/projects/openysm-openysm