Scott Meslow, writing at GQ:
It’s one of many throwaways, when Wayne pops into a music shop to try out a guitar. He starts to jam, but barely get off a few notes before the clerk grabs the neck of the guitar and points to a sign hanging nearby: NO STAIRWAY TO HEAVEN. “No ‘Stairway’! Denied” says Wayne as he turns to the camera. […]
It was only later that I discovered the movie originally included a much more recognizable version of the song—but only in the original cut. At some point after the U.S. release, Warner Music Group and Led Zeppelin refused the rights to even the first few notes of “Stairway” for broadcast, video, or foreign release, resulting in the hasty, patchy edit. “With ‘Stairway to Heaven’ we were told that we could only use two notes before we’d have to pay $100,000, so to sell that he’s gonna play ‘Stairway to Heaven’ in two notes is pretty difficult,” said director Penelope Spheeris.
This article is from 2007, but I had never heard this story before.