hdiutil attach /path/to/imovie.dmg
The drive was labeled, in faded sharpie, "iMovie 1033.dmg". Elara found it taped to the underside of a dead server rack in the sub-basement of the old school. The building was slated for demolition in the morning. imovie 1033 dmg
If the App Store method fails, professional software repositories like MacUpdate or FileHippo often host older versions, though they may redirect you to Apple's servers. hdiutil attach /path/to/imovie