Two co-founders of the plan to build a Muslim community center and mosque in downtown Manhattan have begun exploring a new, and possibly competing, project: an interfaith cultural center that they said might be located at the currently proposed site, two blocks from ground zero, or elsewhere in the neighborhood. Daisy Khan, the executive director of the American Society for Muslim Advancement, said on Tuesday that she and her husband, Imam Feisal Abdul Rauf, two co-founders whose involvement in the controversial community center plan was curtailed this year after a falling out with their real estate partner, might develop a...