answers.onstartups.com pop up after a Google search. I want to verify that it does actually belong to the Stack Overflow family of sites, and that it isn't some kind of cheap impostor. Can anyone confirm?
answers.onstartups.com is now a Stack Exchange Network site.
They are not part of the SO trilogy. They are a customer though.
That is a company/person that has purchased the SO model called stackexchange.
It was created by the founders of SO to license out the SO model to others who wanted to create other question answer websites for other topics. They are not however part of the SO trilogy. They are customers of the SO product and supported on a customer level.
The accepted answer to this question was correct at the time that it was written, but is now out-of-date.
The model described there is now called Stack Exchange 1.0, and it is in the process of being phased out. Existing SE 1.0 sites, such as