Rights can come in conflict with one another, and when this happens one has to yield. The public has the right to open court records, and defendants have the right to know who's suing them. These rights usually outweigh any right the plaintiff may have in suing anonymously. It is possible to sue anonymously in the U.S. (e.g. "Jane Roe" of Roe v. Wade was a pseudonym) but IANAL so I don't know by what standard this is determined or whether the TrueCrypt dev(s) would qualify.