[scaryclam]

As a hiring manager, I wouldn't say people are serious if they have a github account, but having one, which actually has original work in it, can show that the applicant has some interest in the industry beyond the money. If you don't have a github account, that's fine but you've got to show something else that can fill in the gap. Perhaps you're on bitbucket or even source forge. Or maybe you did summer of code. Worst case, tell me you can bring in some samples to an interview.