I somewhat disagree. I think what you wrote in your parenthesis would work as an explanation of open source to plenty of my non-programming friends and they would have an idea of what you're talking about.
Question to friend: You have an idea that computer software is written with code?
[Typical person who has used a computer will respond with something like, Yes, I've heard of computer code.]
Follow-up: Open Source is what we call sharing your computer code with anyone for free. Generally, nowadays, programmers can put their code online for other people to play around with.
Sure, there's more to it than that, but that will give a non-technical person an idea of what you're talking about, and probably makes more sense than what Fox presented. All they needed to add for Github is that it's a company which makes this code sharing easier and more organized and there is business opportunity in making software development easier.