You've stumbled across the master repository for Protonet apps.
If you're looking for apps to install on your Protonet node, then this page probably won't be of use to you. This master repository is installed by default.
But if you're here to see how repositories work, then this might be of interest to you. The source code for all of the official apps is located on our Github organization.
Happy protoneting!
—danopia