In a 2003 lawsuit against the CIA, a group of well-known authors demanded that the agency releases all documents pertaining to the Kennedy assassination, perhaps in an attempt to enlarge its resources for new novels.The word "demanded" indicates the use of command subjunctive for the verb "release"This is a command situation that requires the use of command subjunctive.
Command subjunctive is followed by "that" and consists of the base form of the verb
A. In a 2003 lawsuit against the CIA, a group of well-known authors demanded that the agency
releases all documents pertaining to the Kennedy assassination, perhaps in an attempt to enlarge resources for new novels
B. In a 2003 lawsuit against the CIA, a group of well-known authors demanded that the agency
release all documents pertaining to the Kennedy assassination, maybe in an attempt to enlarge resources for new novels
C. Possibly in an attempt to enlarge resources for new novels, a group of well-known authors, in a 2003 lawsuit against the CIA, demanded that the agency
will release all documents pertaining to the Kennedy assassination
D. In a 2003 lawsuit against the CIA, a group of well-known authors demanded that the agency
would release all documents pertaining to the Kennedy assassination, perhaps in an attempt to enlarge resources for new novels
E. A group of well-known authors, in a 2003 lawsuit against the CIA, demanded that the agency
release all documents pertaining to the Kennedy assassination, possibly in an attempt to enlarge resources for the writing of new novels
Both option B. and E. are grammatically correct, however E. makes the meaning more clear by mentioning "for the writing of new novels".