When “Night of the Living Dead” opened in 1968, mostly in grindhouse theaters, Vincent Canby of The New York Times dismissed it in a three-sentence review as “a grainy little movie acted by what appear to be nonprofessional actors, who are besieged in a farmhouse by some other nonprofessional actors who stagger around, stiff-legged, pretending to be flesh-eating ghouls.” He said the filmmakers were “some people in Pittsburgh.”

As it happened, “Living Dead” followed a trajectory rare in American film: Partly fueled by other, more scandalized reviews (including one by a young Roger Ebert, in Reader’s Digest), it went on to cult success, and two years later was recognized as being sufficiently artful to be placed in the permanent collection of the Museum of Modern Art. Its influence, particularly on the now nearly ubiquitous subgenre of zombie horror (“The Walking Dead” on TV, and the movies “28 Days Later,” “World War Z” and “Shaun of the Dead”) is broadly recognized.

But the filmmakers themselves — the “people from Pittsburgh” who formed a company they called Image Ten to make the low-budget movie — have been able to gain from their groundbreaking work only in a limited way. The film’s original distributor, the Walter Reade Organization (named for its founder, a pioneer of art-house distribution), did not file for a new copyright after changing the title from the original “Night of the Flesh Eaters” to “Night of the Living Dead.” That meant the movie went into the public domain almost immediately. As was once the case with Frank Capra’s “It’s a Wonderful Life,” the movie has been subjected to many unofficial, though legal, iterations.