ONE of the world's most determinedly avant-garde ensembles has turned 40 and shows no signs of becoming staid."It's quite gratifying to do revolutionary theater in revolutionary times, but it's most important to do revolutionary theater in reactionary times," says Judith Malina, who founded the pacifist, utopian troupe with her late husband Julian Beck. The Living Theatre's historical trajectory includes a self-imposed European exile for close to 20 years and a number of run-ins with authorities including the 1963 shutdown of its New York theater for nonpayment of taxes and a 1971 imprisonment in Brazil. Though its impact on the 1960s Zeitgeist and modern experimental theater are indisputable, the anarchist theater collective has endured some scathing reviews in recent years. The troupe's members were disciples of the French surrealist writer and director Antonin Artaud. In the theater's heyday in 1968, the group performed "Paradise Now," which probably set a precedent: The actors assaulted the audience - both physically and with exhortations to "join the revolution."