This week's book giveaway is in the Mac OS forum. We're giving away four copies of a choice of "Take Control of Upgrading to Yosemite" or "Take Control of Automating Your Mac" and have Joe Kissell on-line! See this thread for details.
Well, the safest thing I would suggest is not to touch provided file at all. Personally, I didn't change a single character in that file. For synchronization, I used locks in actual methods instead of making interface methods as synchronized.