DreamShell

Check out the Dream Shell GitHub.

From the GitHub README, edited slightly for grammar:

"The Dreamshell is the operating system for the Sega Dreamcast based on the KallistiOS kernel. It has a dynamic loadable modular system and interface for creating applications with XML UI and both C/C++ and Lua script[s...]. You can see examples in ready-made applications and modules, drivers for various devices, formats and interfaces. Examples for audio and video decoding, compression, packaging, binding, network, emulation, scripts and more. From hardcore low-level assembler to high-level applications. [The ...] large subproject is the ISO Loader, which contains emulation of BIOS system calls, CDDA playback and VMU, also it can [hook] interrupts for various SDKs and more."