GitHub has been a partner of the competition for years now. They help actively promote it, participate in providing feedback to contenders, integrate it with the platform (https://github.com/topics/js13kgames). The competition is organized by https://stars.github.com/profiles/end3r.

But yeah, sure, you're free to tell yourself whatever you want.

And no, it's not only for insiders - thus the message. Outside votes get whitelisted when they meet the compos fairness criteria. It's not a popularity contest. Your vote would not count on this basis (amongst others).