For everyone who isn't a Ning App developer, this won't make much sense to you, but for everyone else, read on:
As a way to reach out to the developer community -- as well as show examples of best practices of OpenSocial based applications that are used internally within Ning -- we have made our Twitter Tracker and Top Friends Ning Apps available via github, through an Apache 2.0 License. This means that developers looking to develop Ning Apps for the first time can take a look at how our team has built some of the Ning Apps used across the millions of Ning Networks available today, and it offers an opportunity for more advanced Ning Apps developers to contribute features and bug fixes, by forking from the central repository.
You can find the repositories here:
Top Friends: http://github.com/ning/ningapp-topfriends
Twitter Tracker: http://github.com/ning/ningapp-twittertracker
Our hope is to have additional Ning Apps available for the developer community soon. Stay tuned!