Ask HN: What is this software "Clash"?

This is a fork of the original project by dreamacro. Original one has been removed somehow. https://github.com/Ieooo/clash

It seems that it's capable of tunneling network and doing some proxy stuff. I see these kind of repositories forked from Clash, and repositories related to clash, such as dashboarding software and desktop app on Github Trending RSS very frequently.

What is happening with this? Is China government censoring this software or something?