If I replicate the brain algorithm of a human, but I do it in some other form (e.g. as a computer program, instead of using carbon based molecules), is that an "AI"?

Possibly, that's a borderline case.

If I make something very very similar, but not identical to the brain algorithm of a human, but I do it in some other form (e.g. as a computer program, instead of using carbon based molecules), is that an "AI?"

In my original reply my intent was "provided that there are no souls/inputs from outside the universe required to make a functioning human, then we are able to create an AI by building something functionally equivalent to a human, and therefore strong AI is possible".

Even if humans are essentially computable, in a theoretical sense, it doesnt follow that it is physically possible to build something functionally equivalent on a different type of hardware, under practical constraints.
Think of running Google on a mechanical computer like Babbage's Analytical Engine.