Simple DNS Plus has a plug-in system for providing additional/optional functionality. This allows us and 3rd parties to develop new features without cluttering the base product, and allowing users to select which of these features they want - or don't want.
The standard Simple DNS Plus installation comes with a number of plug-ins, more can be downloaded.
For more information see http://simpledns.com/plugins
Plug-ins are instantiated in the Plug-Ins instances dialog.
Some plug-ins (including the DHCP Server plug-in) have their own View - a dockable sub-window in the main window.
The plug-in architecture is open for users and 3rd parties interested in developing their own plug-ins.
In short, this is all based on the .NET Framework 2.0 interfaces found in the "sdnsplugin.dll" file supplied with Simple DNS Plus. More information about developing plug-ins is available on-line at http://simpledns.com/kb/31.