As an interviewer I only look at the resume and published open source projects the candidate did.
Everything else just a random impression, nothing serious to bother.
The questions are for something else.
I like this approach the most. Evaluate code that they've already written, maybe make sure that they can solve a similar problem to make sure they actually understand what they did and didn't pay someone else to do it, and then a personality fit. Chances are if they really wanted to be hired to learn how to program they're aware of the importance of contributing to open source.
This is frustrating for the many engineers who have no open source work. You're shutting out a massive amount of talent that has only worked on proprietary software.