At one point, I was able to download and install Darwin OS from the Apple open-source website. I was able to download Darwin 8.0.1, which is the base for 10.4 (Mac OS X Tiger). If I remember correctly, it was around the time of Leopard (10.5). I cannot find the download link now, but it ran in single user mode, and I didn't continue on to installing an actual GUI. Found the link from: (direct download). You can also take a look at the project: One current goal of this project is to provide a useful bootable ISO of Darwin 10.x and Darwin 9.x. The 'current' versions of Darwin are 12.4.0 (OS X Mountain Lion 10.8.4), 13.0.0 (iOS 6, and OS X Mavericks), and 14.0.0 (iOS 7), so these are definitely older versions.
Darwin 10.0 is Mac OS X Snow Leopard/iOS 4, 9.0 is Mac OS X Leopard/iPhone OS 1, and 8.0 is Mac OS X Tiger/Mac OS X for Apple TV. I'm not sure if this is a good question for Ask Different, maybe Server Fault would be better? My understanding is it's a complete UNIX server environment but there is no tech support available from Apple or anyone else, and generally the only people who know how to use it are people who contribute code to the project. You should be able to install it on any x86 system, I'm not sure how.
This is the current version of VMware Tools for OS X from the VMware CDS. Instructions for extracting darwin.iso - Download the. Does this run in Mac OS X 10.6.
You'll get a standard unix shell on boot and have to create users and install some kind of package manager, then install Gnome or something. Window Maker might be fun.