|  | Leopard  Technical Notes:  Mac OS X Server Darwin Darwin is the open source UNIX-based foundation of Mac OS X Server. Darwin integrates a number of technologies. Among the most important are the Mach 3.0 microkernel operating-system services, based on 4.4BSD (Berkeley Software Distribution), the high-performance networking facilities, and the support for multiple integrated file systems. For Mac OS X Server, developers can use Darwin to create modules that operate at the kernel level. |