Mixcraft 6 Home Studio can't open Mixcraft 6 projects because Mixcraft 6 has a bunch of extra features that are not backward compatible
, like submix tracks, for example.
You can load the audio files from the Mixcraft 6 project into Home Studio, or if you're working with virtual instrument tracks, your friend could save the project as a .mid file and send it to you.
And of course, you could also upgrade to Mixcraft 6 by clicking on the Upgrade option at the top of Mixcraft 6 Home Studio's screen. That costs $40.