[qnm]

Github[0] gives Junior developers another way to get an interview. Those with minimal professional experience are able to show - to some degree - that they can code, use a VCS and have an understanding of the push/pull/fork contribution model. Bonus points for contributions, bug reports etc.

I don't believe it replaces one, but for those without a well-seasoned resume, a Github profile works well as a conversation starter.

[0] Or any public VCS, of course.