On the 9lessons.info site they've posted a new tutorial showing you how to login with GitHub via OAuth via a custom script.

Nowadays GitHub.com(web based hosting service) is the most import part in developer’s life. In this I want to discuss how to implement GitHub OAuth login system for your web project, this is very simple adopt and sure it will helps you to increase your web project registrations. Please check my previous posts for Google, Facebook and Instagram OAuth login system scripts.

The system uses a simple database to store the current user information and their Github ID. They walk you through the flow of creating a new application on the Github site and include the scripts to make the initial request, redirect to the Github site for authorization and handle the callback correctly.