http://boards.theforce.net/threads/darth-maul-wasnt-cut-in-half.16593500/

Looks like this is an old rumor, mostly based on a few people not remembering it happening. In 2004 there was a short blurb where someone claimed it to be true: https://web.archive.org/web/20040727113927/http://cgi.theforce.net/theforce/tfn.cgi?storyID=5121

Looks like the origin of that image. Supposedly, it was an alternate version made in case it needed to be changed to get the rating they wanted. But there’s nothing that convinces me in that poorly written “article”. Not sure what “an THX screener’s report card” is supposed to mean, and I’m not convinced that a 300x300 pixel image isn’t doctored just because they say it isn’t.

Even if they really made this version, I doubt anyone saw it in theaters. I think it’s just another grappling hook phenomenon. Maybe people mis-remembered because it was a terrible Yosemite Sam style death where the body took a second or so to fall in half.