I moved your question to the forum as there might be others that have this question. I hope this is OK.
A Go! app, a.k.a. a "single-issue app", is an app that you can only publish one issue in. This is how it works. In our Publish portal you build your app, this app build only contains your icons and the help guide (explaining how to navigate the app). In our Portal you also upload your issue which is placed on our server, this issue is not included in the app when the user downloads the app of the AppStore but as soon as the app is started the app will automatically start downloading the issue of the server.
A good example of such an app is UN:LIMITED ( http://itunes.apple.com/se/app/the-unlimited-magazine/id498743060?mt=8)
Here are some step-by-step tutorials for building the different apps you can build with Mag+: http://support.magplus.com/entries/21045691-build-your-ipad-app-tutorials
Let me know if there's anything else you would like to know!