Are you sure abut that?
It that's true, it's a ripoff!
The new iphone has so many new features there really is no need to make something like an imovie app exclusive to it.
Would be just like last year when they for some reason didn't let 2G users send MMS or 3G users use voice control...
hell, I'm never sure about anything, but here are some of the quotes from the page.
"Built just for iPhone 4, iMovie lets you combine and edit video clips, polish your movies with dynamic themes and transitions, add music and photos, and share your finished movies with the world."
"Make beautiful HD movies anywhere with iMovie, the fun, feature-rich video editing app thats designed for iPhone 4. "
"Get the iMovie app and start editing movies on your iPhone 4. Coming soon to the App Store for $4.99."
"The iMovie app was designed specifically for the Multi-Touch technology on iPhone 4."