# KallistiOS

> unofficial operating system for the Sega Dreamcast

**Wikidata**: [Q1722492](https://www.wikidata.org/wiki/Q1722492)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/KallistiOS)  
**Source**: https://4ort.xyz/entity/kallistios

## Summary
KallistiOS is an unofficial operating system for the Sega Dreamcast, developed as a homebrew project. It provides a development environment for creating software and games for the console, allowing users to run custom applications beyond the original Dreamcast firmware. The project was named after the Apple of Discord, a mythological fruit associated with strife, reflecting its unofficial and community-driven nature.

## Key Facts
- **Type**: Unofficial operating system for the Sega Dreamcast
- **Aliases**: KOS, Libdream
- **License**: 3-clause BSD License
- **Latest stable version**: 2.2.1 (released 2025-09-20)
- **Inception**: 2000
- **Named after**: Apple of Discord (mythological fruit)
- **Source code repositories**: GitHub (https://github.com/KallistiOS/KallistiOS) and SourceForge (https://sourceforge.net/projects/cadcdev/)
- **Website**: http://gamedev.allusion.net/softprj/kos/
- **Instance of**: Operating system, programming tool
- **Use**: Homebrew development for the Sega Dreamcast

## FAQs
### Q: What is KallistiOS used for?
A: KallistiOS is used as a development platform for creating and running custom software and games on the Sega Dreamcast. It allows users to bypass the console's original firmware and execute their own code.

### Q: Who developed KallistiOS?
A: KallistiOS was developed by a community of enthusiasts and programmers, with no single creator attributed. It is an open-source project hosted on GitHub and SourceForge.

### Q: Is KallistiOS legal to use?
A: Yes, KallistiOS is legal to use as it is an unofficial, open-source project. However, users should ensure compliance with Sega's terms regarding homebrew development for the Dreamcast.

### Q: What hardware does KallistiOS support?
A: KallistiOS is specifically designed for the Sega Dreamcast, providing a software environment that interacts with the console's hardware.

### Q: How can I contribute to KallistiOS?
A: Contributions to KallistiOS can be made through its GitHub repository (https://github.com/KallistiOS/KallistiOS), where developers can submit code, report issues, or suggest improvements.

## Why It Matters
KallistiOS played a significant role in the Sega Dreamcast's legacy by enabling homebrew development, which extended the console's lifespan and allowed for creative experimentation beyond official software. As an unofficial operating system, it provided a platform for developers to explore the Dreamcast's hardware and create custom applications. The project's open-source nature fostered a community of enthusiasts who contributed to its evolution. Today, KallistiOS remains an important resource for retro gaming and development, preserving the Dreamcast's legacy and offering a unique development environment for its architecture.

## Notable For
- **Unofficial OS**: One of the few unofficial operating systems developed for the Sega Dreamcast.
- **Homebrew Development**: Enabled the creation of custom software and games for the console.
- **Community-Driven**: Developed and maintained by a community of enthusiasts and programmers.
- **Open-Source**: Released under the 3-clause BSD License, allowing for widespread use and modification.
- **Named After Mythology**: Named after the Apple of Discord, symbolizing its unofficial and community-driven nature.

## Body
### Overview
KallistiOS is an unofficial operating system designed for the Sega Dreamcast, developed as a homebrew project. It provides a development environment for creating software and games for the console, allowing users to run custom applications beyond the original Dreamcast firmware. The project was named after the Apple of Discord, a mythological fruit associated with strife, reflecting its unofficial and community-driven nature.

### Development and History
KallistiOS was initiated in 2000 by a community of enthusiasts and programmers. It has since evolved through multiple versions, with the latest stable release being 2.2.1, published on 2025-09-20. The project is hosted on GitHub and SourceForge, where developers can contribute to its development.

### Technical Details
KallistiOS is licensed under the 3-clause BSD License, which allows for widespread use and modification. It is classified as both an operating system and a programming tool. The project's website, http://gamedev.allusion.net/softprj/kos/, provides resources and documentation for developers.

### Significance
KallistiOS has been notable for enabling homebrew development on the Sega Dreamcast, which extended the console's lifespan and allowed for creative experimentation beyond official software. Its open-source nature has fostered a community of enthusiasts who have contributed to its evolution, making it an important resource for retro gaming and development.

## References

1. [Source](http://gamedev.allusion.net/softprj/kos/faq.php)
2. [Release 2.0.0. 2013](https://github.com/KallistiOS/KallistiOS/releases/tag/v2.0.0)
3. [Release 2.1.0. 2024](https://github.com/KallistiOS/KallistiOS/releases/tag/v2.1.0)
4. [Release 2.1.1. 2024](https://github.com/KallistiOS/KallistiOS/releases/tag/v2.1.1)
5. [Release 2.2.0. 2025](https://github.com/KallistiOS/KallistiOS/releases/tag/v2.2.0)
6. [Release 2.2.1. 2025](https://github.com/KallistiOS/KallistiOS/releases/tag/v2.2.1)