COBE is a new operating system under BSD license, so everyone has free access to sourcecode.
The goal of COBE is a microkernel, which is to represent only the most necessary functions efficiently available. Also, the system should be kept to below the 10 MB limit (currently about 100 KByte).
COBE is currently at version 0.1 Alpha
The current image of COBE 0.1 Alpha unstable can be found under Downloads
The current sourcecode can be found here.
A documentation of the sourcecode can be found here (not completely yet)
A User-Manual can be found here (only in German yet)