GitHub is a fantastic source code management tool, but the most interesting thing about it is that it’s a social coding repository. What GitHub allows you to do is share code in such a way that people can clone your code repository. They can make improvements or fork the examples into an entirely new form, and then share those changes with the rest of the world in a very transparent way.
If you look at the project I started on GitHub, you can see exactly who did what with the code, whether I incorporated their changes back into my own repository, whether someone else has done something novel by using an example listing as a template, etc. You end up with a community of people that emerge around common causes, and amazing things start to happen as these people share and communicate about important problems and ways to solve them.
A great observation from Matthew Russell on why he opted to use GitHub to share the examples of his book.