It was like fate that the word dual jumped out at me while fanning to get to the page I was headed to.
If you kept fanning to page 189, you'd see that the Heritage Guide has an entire section entitled "Presidential Eligibility." Wherein it states, on page 190:
"Under the longstanding English common-law principle of jus soli, persons born within the territory of the sovereign (other than children of enemy aliens or foreign diplomats) are citizens from birth. Thus, those persons are "natural born citizens" and eligible to be President."
It says absolutely nothing about a dual citizenship bar. The definition of "natural born citizen" as provided by the Heritage Guide explicitly confirms that Obama is a natural born citizen.
Interesting reading about Terri/Donofrio and Hawaii cover up: