From what I understand based on HN comments over the years, HN proper has lots of special secret sauce to prevent spam, voting fraud, etc.
It's shipped with Arc, a programming language pg made. So yes, it is open source.
Out of curiosity, what voting algorithm are you using at the moment? You'll have to tweak it if the site takes off. Especially since people get very particular about politics, even more so than money, and will try to game it in whatever way possible. It could make HN voting rings look benign.
I'm not the site creator so you'd have to ask him.