Microkernel manages hardware, provides some services to core kernel, a Java Virtual Machine (JVM), to support fuzzy logic (claims first OS to do so), object-orientation, parallel and distributed processing. [Open Source, GPL]

Modular object-oriented application to index files across networks. Consists of plug-in type data retrieval system, webserver, peer-to-peer connections for network-wide information gathering, retrieval; has features of OSs, database management systems, distributed networking. [Open Source, GPL]

Delicate + Smalltalk; true OO OS, based on Smalltalk concept, intended to be testbed for fresh ideas in computing. Small description, downloads: source, binary, clock. Tar.Gz file. [Open Source, GPL]

Component-based multiuser OS; message-based programming, threadless execution, virtual filesystems to be fully modular programming environment. Some code, clear explanations of design and philosophy. [Open Source]

Official site of GNUstep: free implementation of NeXTStep/OpenStep specification.

Component-based OS, runs natively on i80386+ based PCs. Has novel protection mechanism allowing more OS decomposition and high performance: protection overheads almost 1,000 times less than normal OSs. [Open Source, GPL]

For developers; want those who like ASM, C/C++ and wish to make an OS for enjoyment and useful tasks such as routers, web servers; full documentation, FAQ, history, news, buglist, downloads, forum. [Open Source, GPL]

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]

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

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]

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]

Orthogonally persistent, capability-based secure SASOS using L4 2nd generation microkernel. Goals: Prove SASOSs can run on normal hardware, be as secure as normal OSs; can be as efficient as, and are faster than, normal OSs in some important uses; can be pure SASOSs with all data (even system data) in one address space and no other IPC mechanism is supported by OS. POSIX emulating. [Open Source, GPL]

Object-oriented OS uses best parts of VMS, Unix, Windows NT. Almost everything in kernel is an object (threads, processes, devices, files, event flags, more) to which one can assign logical names. [Open Source]

Multitasking environment, written in Java, for all Java programs, can execute many Java applications in unique virtual machine. Descriptions, screenshots, downloads. [Open Source, GPL]

Plugin-based architecture: if a feature is unneeded, don't download it or waste storage; Linux and Windows compatible; GUI driven, fully skinable to alter its look; includes voice recognition, interactive help system. [Open Source]

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

Lightweight, very modular component-based, multitasking, embedded OS; developed, used for many research projects. Goal: manage fast data streams in multimedia environments; for speed and low overhead has zero copy architecture: passes pointer references to data instead of copying it. [Open Source, GPL]

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]

Object Operating System, OOS, pronounced ooze; goal: create new OS architecture, which uses filesystem to do many jobs usually done via various means. Design philosophy inspired by Unix, Plan 9, but does many things uniquely, trades compatibility for simplicity. [Freshmeat]

Modern object-orientated microkernel, focus: flexibility and functionality, instead of speed and compatibility. Coded in C. Description, downloads. [Open Source, GPL]

Claimed as radical new approach to OSs: no-kernel, self-modifying cells (like objects); single address space, useful where memory and CPU power is low, and maybe for AI. Written in self-modifying, modular assembly language. [Open Source, BSD]

Object-based framework to implement network protocols; defines an interface that protocols use to invoke operations on one another (i.e., to send messages to and receive messages from adjacent protocols) and a collection of libraries to manipulate messages, participant addresses, events, associative memory tables (maps), and threads.