San Mateo-based SuccessFactors, a developer of business management software, said Thursday that it has acquired Inform Business Impact, a developer of workforce planning tools. SuccessFactors said it would pay $25.5M in cash plus approximately $15M in its common stock for Inform, along with unspecified contingent payments. Inform's customers include Comcast, BHP Billiton, Starbucks, Nike and ANZ Bank.