Two prominent MIT figures began seeking signatures on Thursday for a letter criticizing the university for failing to support four students facing a New Jersey fraud investigation. But by the evening, MIT said that, in fact, it is “eager” to help the students. The letter, addressed to MIT President Rafael Reif, said MIT’s lawyers told the students they wouldn’t get involved in a matter that didn’t directly involve the university — an echo of the tragic case of Aaron Swartz. “Students are being threatened with legal action for doing what we encourage them to do: explore and create innovative new technologies,” wrote Hal Abelson, a computer science professor; Ethan Zuckerman, director of the Center for Civic Media; and Media Lab graduate student Nathan Matias.