Odiseo Desktop
Multitasking environment, written in Java, for all Java programs, can execute many Java applications in unique virtual machine. Descriptions, screenshots, downloads. [Open Source, GPL] You Would also find info related to odiseo java free open source desktop odiseo jexplorer operating system GPL GNU and much more.

E-Leos
Typed OS to very securely execute programs, which can only manipulate defined type variables, not memory spaces; avoids many problems caused by programming in languages such as C. French initiative, binary fits one floppy disk. [Open Source]

JNode
Description, downloads, CVS, bug track, support. [SourceForge.net]

JNode
Goals: all Java OS, flat memory model, for personal use, simple to use and install, any Java applications to run on it fast and safe. Descriptions, documents, screenshots, downloads. [Open Source, LGPL]

JOS: Java Operating System
Collaborative undertaking by an international group of Java programmers and enthusiasts to create free Java OS. [Open Source]

JX Group
JX OS: set of Java components executes on core doing system initialization, CPU context switching, low-level domain management; code organized as components loaded into domains, verified, translated to native code; protection based on only type safety of intermediate (byte)code. [Open Source]

leJOS
Tiny Java OS for Lego RCX brick. Like its predecessor TinyVM, has tiny Java runtime, under 32K; works as replacement firmware for Lego; Hitachi H8300 processor. To be ported to more small devices. [Open Source, Mozilla] You Would also find info related to leJOS, Java, TinyVM, Lego, Mindstorms, RCX, Robots and much more.

RCOSjava
Tool designed to teach inner workings of operating systems: simple animated simulated OS and hardware coded in Java. RCOS successor.

Sanos
Minimal OS kernel for PC based server appliances. Lets you run java server applications without need to install host OS, only need normal Java HotSpot VM and Sanos. Description, documents, downloads, manifesto, links, contact. [Open Source, BSD]

SavaJe Technologies
Makes SavaJe XE OS: based on full Java 2 Platform, Standard Edition (J2SE), for smart phones, advanced wireless handheld devices, web pads, other Internet appliances.

Websprocket, LLC
Makes LogOS: Linked object generation Operating System, and other Java on bare metal synthesis technology for embedded systems. Tools to make dynamic, classloadable programs without overhead of traditional OS and JVM software layers.