Yepp.
And, by the way, the source of HN is open, everyone can read how it works =)
No, then it wouldn't be secret anymore.
Security by obscurity is not perfect but in this case having that knowledge out there would only benefit the spammers and the 'gamers'.
Is news.ycombinator.com open source ?
Yes it is, the code is written in a language layered on top of scheme called 'Arc', you can get the whole package here: http://arclanguage.org/ , the package includes a slight variation (the 'secret sauce' is missing) on the code running HN.