San Bruno, CA-based marketing software provider Responsys (NASDAQ: [[ticker:MKTG]]) finished its first day of trading Thursday at $15.40 per share, up 28 percent over Wednesday night’s initial offering price of $12 per share. Share prices were holding steady in early trading Friday. Early investor Entrepreneurs Fund cashed in some of its stake through the offering, but the company’s other investors, including Accel Partners, Foundation Capital, Redpoint Ventures, and Sigma Partners held out, according to a report in Dow Jones VentureWire.