UnixLite -- A LightWeight Unix Operating System Written in C++ targetting to eduation and embedded was released on Jun 1st 2006. It's developed by China 南京航空航天大学 (NUAA). The kernel is quite small, up to 20,000 lines of code. The license is GPL. And it has completed the common system calls, furthermore, it is binary compatible with linux, and some GNU software have been ported to unixlite.

I listed the main features here (copied from their website)

• Support paging and flat memory model, nearly same as linux
• Implements about 80 posix compliant system call
• Binary compatible with linux
• Able to run bash/gcc, and some other common UNIX tools
• Very rudimentary TCP/IP support, able to run a simple http server
• Very small, about 20000 lines of code
• Written in c++, highly modular and extensible
• Minix's 32-bit file system

Very expecting!

Here is one screenshot for running webserver in unixlite.