You can download the current version of DotNetNuke from this
link. I became familiar with DotNetNuke
when it first was developed from the IbuySpy
portal. The early versions gave you a quick way to setup a portal on your web using
the new .NET Framework 1.0. The benefits were a quick way to setup your web
site, with the ability to register users baked in; no programming was
necessary. Also, there were announcements and the ability to allow end users to
edit content, again without programming.
Developers could modify the source code of DotNetNuke to
customize it how they wanted. While it is programmed in VB.NET, C# modules can
be created. Developers could create custom modules containing the look and feel
of the portal. Changing that look and feel was not an easy change but it could
be done site wide. The main power of the original DotNetNuke, I believe was the
ability to create separate portals within one DotNetNuke application with
different content. The original IBuySpy would not easily let you do this
without modifications to the code.
Originally, DNN supported SQL Server as the backend. As new
versions have been created, DNN has created more ways to connect with other
data stores. Later versions also make customizing the look and feel of a portal
an easier task.
The current DotNetNuke has taken these concepts much
further, and in a slicker package. Besides more modules to choose from in the
default package, the design in DNN has progressed also. For developers, they
are using a Provider Pattern for data access. If you need details on that feel
free to look at their documentation found here.