The osFree project
We're all aware of Haiku, the open source re-implementation of BeOS. This week, I found out a similar effort is underway to recreate OS/2 Warp 4 as an open source operating system.
osFree is a Free Open Source software operating system development project, aiming to replace eventually all OS/2 subsystems with Open source analogues. It aims for OS/2 Warp 4 (Merlin) as a base compatibility system, which does not mean that we will not support features of newer (OS/2 Warp Server for e-business, eComStation and ArcaOS) OS/2 versions. This includes rewriting not only user-level code but the OS/2 kernel too.
The project is very much in its early alpha stages, so don't expect to boot into osFree any time soon. That being said, they have made progress over the years, and their current status explains how far along they are.
osFree project is deep in the alpha stage. At the present time the osFree project work with low-level parts of operating system like loader and related tools. We also try to develop an experimental prototype of OS/2 personality for L4 microkernel. Also we have set of command line tools like CMD.EXE and file/disk maintenance utilities.
I absolutely adore OS/2, and while I understand all too well a project like this won't be finished overnight - look at Haiku - I do love that it's being worked on.