Nope. It's a clone, or a site that looks similar, but is not part of the Stack Exchange network. All SE sites are under the
stackexchange.com domain name.
The following sites have their own domain name because they are older:
There is also AskUbuntu.com, a special exception that was formed because of a partnership between Ubuntu and Stack Exchange. However, this sort of relationship does not happen anymore (there was a dedicated facebook dev site, but that was phased out). You have to go through Area 51 to get a site approved.
And, there is MathOverflow.net, which was started as an SE 1.0 site in September 2009. It eventually joined the network in June 2013, yet it is still owned by the independent entity MathOverflow and its presence in the network is governed by an individual agreement.
Plus, they have double diamond users. What does that even mean???