Take this URL: https://help.github.com/articles/installing-an-app-in-your-organization/
Title: Installing an app in your organization
Yet the next line says:
You can install apps from GitHub Marketplace to use in your organization.
This implies that you cannot install non-Marketplace apps in your organization.
Similarly, once you scroll to the steps:
Is there a document that actually describes how to install an app and doesn’t confuse users with Marketplace? I understand GitHub would like to focus on the revenue-generating Marketplace but this page in particularly is far too confusing and should be renamed or fixed. Please don’t treat non-Marketplace apps as second class citizens.