Due to a technicality arising from now defunct copyright laws that stated copyright information must be included in a film's credits, they were able to use footage from the original Night Of The Living Dead without permission.
Besides the obvious scene recreation and clips used from the original Night of the Living Dead, this movie is just one big homage to the 60s classic. Several characters are named after cast/crew members of the original Night of the Living Dead (Duane/Duane Jones, Judith/Judy O'Dea & Judith Ridley, Russell/Russ Streiner, Keith/Keith Wayne, Karl/Karl Hardman, Kyra/Kyra Schon, Marilyn/Marilyn Eastman) and a few others are named after characters (Judith/Judy, Karen, Benjamin/Ben). Additionally, Bill Hinzman, who was in the original NotLD has a cameo in this film.