The desktop server is a Windows application that runs within your current, interactive login. It is intended for evaluation and testing only. Unlike the BBS service, it cannot accept callers unless you remain logged into Windows. However, it does allow you to quickly test the BBS without the burden of a complex installation.
You may run the desktop server at the same time as other servers (including the Windows Service). This is useful when you are attempting to configure a new door game (or other external program). Since you are testing under your interactive login, you will be able to see any windows created by the external program.
However, there is one catch: Only one program can bind to a particular TCP or serial port at any given time. This means you will need to configure the desktop server to use a different (non-standard) port for accepting incoming connections. This is necessary only if you run the desktop server at the same time as another server that is already bound to a port.