Github is a platform for putting source code on the Internet, which has taken over the rough-and-tumble computer engineering world. Its genius is threefold.
First, it’s affected a dramatic increase in open source code, by providing easy free hosting for open source projects.
Second, it’s given engineers and organizations a way to profit from small projects beyond selling licenses, just by making it easy to keep track of (and thus to assign credit for) contributions to codebases.
Third, it’s opened up easy channels for (technically oriented) end users to make small contributions to codebases, dramatically increasing the body of open source contributors.