Less than a month after he returned to take the post of vice chairman, Cullinet Software Inc founder John Cullinane has reassumed the posts of chairman and chief executive, replacing his successor David Chapman who has resigned, but will continue to consult for the Westford, Massachusetts system software company. Responsibilities of president and chief operating officer George Tamke have been expanded to include development, legal, and finance and administration. Tamke was previously in charge of sales, service and marketing worldwide.