This is the source for my Getting Started with Services Framework WebAPI edition blog post.
You can find it here.
Install DotNetNuke 7.0 or later then while in the DesktopModules directory of your site execute the following command:
git clone https://github.com/sschlesier/sf-webapi-helloworld.git MyServices
Now you can load the solution into Visual Studio and compile or edit as you see fit.