Software to setup similar to Y Combinator

I think it doesn't matter what you use. Could literally be anything.

From simple server using something like Python/Ruby/Go/... To using JS front-end with simple API.

You probably need a database.

Thank you. I mean i wanted a open source software to host similar site and don't want to develop anything

If you aiming for community discussions and link sharing, first things that come to mind is https://www.discourse.org/

No. I want to setup my own like the same one as YC

Discourse is open source forum/discussion software that you can host yourself. Youcan also find services that will host it for you for a price.

You can use an older version of the same codebase here: http://arclanguage.org.

The closest clone I can think of is Lobsters[1,2]

https://lobste.rs/ looks great + open-source. I particularly like their invite-only system.

you can view the frontend source with your browser