The man, known only as M.B., has asked a judge to reverse his order to turn his name over to attorneys representing Tyler Clementi's roommate.
M.B. told the judge in a written statement he fears his name will leak out.
The judge ruled that prosecutors must disclose the name to Dharun Ravi. Ravi is accused of bias intimidation and other charges.
Clementi committed suicide days after the alleged webcam-spying incident, triggering a national conversation about bullying of young gays.
M.B.'s attorney, Richard Pompelio, told The Star-Ledger of Newark the intense media interest in Clementi's death is one reason why M.B. doesn't want his identity revealed.
Information from: The Star-Ledger, http://www.nj.com/starledger