“You don’t call four people a generation,” argues poet Gregory Corso at the outset of What Happened to Kerouac?, a 1986 documentary by Richard Lerner and Lewis MacAdams that’s been reissued on DVD by Shout! Factory with two and a half hours of interview outtakes. Corso may be right, but an endless series of movies have been drawn from the relationships among Jack Kerouac, Neal Cassady, Allen Ginsberg, and William S. Burroughs. Two more are on their way down the pike as I write: On the Road, Walter Salles’s adaptation of Kerouac’s roman a clef novel, premiered at the Cannes film festival in May and is scheduled for an Oscar-qualifying run in December. Next year brings John Krokides’s Kill Your Darlings, which dramatizes the 1944 homicide in New York City that involved Kerouac (Jack Huston), Burroughs (Ben Foster), and Ginsberg (Daniel Radcliffe) as witnesses.