BOSTON — The Massachusetts Lottery is considering developing a daily fantasy sports game as the online competitions have exploded in popularity – and faced increased scrutiny about their legality. Michael Sweeney, the lottery’s executive director, said exploring options amid such games’ legal ambiguity is necessary if state lotteries are to remain viable in a changing gambling landscape. “Until such time as it becomes absolutely clear that this is illegal, we have an obligation to really grapple with the potential,” he said.