Can I disable Double Opt In for Forms or API?

Can I disable Double Opt In for Forms or API?

I am used to allowing my subscribers to fill in the form and then be added to the list. Is there a way to remove the double optin?
I would prefer to use the built in forms but would also be fine using the api if it allowed such a thing.

Does this code in the forms apply to disabling the optin:

_setOptin(false


I include unsubscribe links in all the autoresponders.