stackoverflow clone or paid feature? [migrated]

I was looking for something related to nest.js and in one of the results in the google search was this thread. It's a StackOverflow thread but on a website with domain http://jtdz-solenoids.com! How?

What is this website? Is it one of the paid features of StackOverflow? I'm just curious about how it can have the same UI. I'm not even sure this question belongs here as I don't have any particular tag to categorize this question. Please point me in the right direction if this question violates any rule.