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

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]
   http://lejos.sourceforge.net/

SavaJe Technologies  
   Developer of SavaJe OS for advanced mobile phones. Offers company overview and list of partners.
   http://www.savaje.com/

RCOSjava  
   Tool designed to teach inner workings of operating systems: simple animated simulated OS and hardware coded in Java. RCOS successor.
   http://sourceforge.net/projects/rcosjava/

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]
   http://www.jbox.dk/sanos/

JNode  
   Description, downloads, CVS, bug track, support. [SourceForge.net]
   http://sourceforge.net/projects/jnode

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]
   http://www.geocities.com/innigo.geo/

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
   http://www.jxos.org/

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]
   http://leo.e-leos.net/