Yosemite and FCP7? Compatability?
Final Cut Pro 7 does work on OS X Yosemite.

Check out ProVideoCoalition's post that detailing the installation of FCP7 on OS X 10.10; Installing and editing with Final Cut Pro 7 on a new Macbook Pro with Yosemite


  Overall the edit went very well. Not a crash, not a peep from Final
  Cut Pro 7.0.3.
  
  Oh, and that was running Yosemite version 10.10 so we know Final Cut
  Pro Classic is still working on Apple’s latest operating system.


Multiple users on Apple Support Communities have said the same;


  cameradude2
  
  Does anyone know if Final Cut Pro 7 work in the new Yosemite upgrade?
  
  Mer the Dog 
  
  It does on my system...