Emeryville-based Alibris Holdings, which operates the Alibris online marketplace for new and used books, said Tuesday afternoon that it is acquiring Monsoon, an Oregon firm which develops online marketplace software. Financial terms of the buy were not disclosed, however, Alibris said the deal consisted of both cash and stock in Alibris. Private equity firm Oak Hill Capital, which owns Alibris, is providing funding for the deal, which also includes bank financing from Square 1 Bank. Alibris said it will hire on Monsoon CEO Kanth Gopalpur, and will continue to operate the two firms as separate businesses. Alibris was advised by Wilson, Sonsini, Goodrich & Rosati in the deal. Monsoon was advised by Tonkon Corp.