Apple - Is there a free QR code reader for Mac?
I just discovered QR Journal, which works fine for me. The latest version requires OS X 10.8/10.9 but there is a legacy version available which works with 10.6.
Now desktop users with an iSight (or iSight compatible) camera can read QR codes. Found a QR code in a magazine or catalog? Simply hold up to the iSight camera to scan, store and browse to. Received a QR code in an email? Just drag it into QR Journal to read it.
There is an Adobe Air application you can download called QR Reader - works on any platform that has Air installed, and a bunch of online services you could try too - QRGen looks pretty neat - you upload an image of the QR code and then it processes it for you.
Hope that helps.
No free app that I'm aware of, but for a few dollars/euro you can download QuickMark from the Mac App Store, here's the link