This is particularly useful if you want to run a match between two engines, and you'd like them to run on separate machines so that they do not have to compete with each other for memory and processor time. Unix normally comes with an rsh server, so xboard and WinBoard have always been able to control remote engines running on Unix machines, but working rsh servers for Windows are hard to find. Dan's server should fill this gap. It is not a complete implementation of rsh, but Dan says that it implements enough to work with WinBoard. You can read the documentation and download the rsh server here.
Source code is included.
If you want to write a chess engine in Delphi that works with WinBoard, Tony Werten has donated some sample code that should help you get started.