Yes, Avid Media Composer 2.8 runs great on Leopard. GeniusDV has posted a work-around for running Avid Media Composer on Leapord I tried this myself and it actually works.
Also, the article mentions about NOT downloading the latest version of QuickTime. I accidentally ignored that part, and the software still seems to work.
FYI: With the newer Macs it is not possible to downgrade them to run 10.4 (Tiger). The only work-around to be to downgrade the firmware, of which you’ll need to contact Apple Support for that.