DotNetNuke should be able to satisfy your needs. The core system already contains a bunch of modules that might be useful for your purposes, or else there are several third party modules available that specialize exactly in what you want. You might want to have a look at www.ventrian.com, they have a nice articles module, but there are others available at the DNN market place (here on this website) or at www.snowcovered.com.

As to the source code being available -- DNN is completely open souce, with a very generous license, and many of the third party modules are also available in a source version.

Enjoy DNN!

 Vera

You should get yourself the Install Package. It contains everything you need to run DNN in a production environment, including all core modules. If you're using the Install Wizard, you'll be prompted to select modules you want right away, but you can also skip that step and install them later on from the Host > Module Definitions page. (The files will be installed already, only they are not yet "linked" to the installation, as to save overhead.) My recommendation would be to start with only a few modules (Text/HTML, Links, News) and add others as you find the need for them. Not installing unnecessary modules improves preformance!

You should also get the Documentation Package. This is only listed in the section for 4.5.5 downloads, and has yet another version number in the file name, but don't let yourself be confused by that. Those basic infos don't change that often. Installation procedures etc. are still the same. The Docs Pack has an installation guide and a lot of other information that may be useful as you're getting more and more into running, developing and skinning DNN.

Enjoy!
Vera