You already have it. Articles is built using the WSP (website project) model where the code is included as part of the install and ASP.NET compiles it at runtime. There is no separate compiled DLL.

To make changes to the code, just install the module the way you install any DNN module. You will then find the .vb files in the DesktopModules/Articles and App_Code/Articles directories. You can make changes to the code while the site is running and just refresh the page to see your changes. ASP.NET 2 does the compilation in the background