I'm the only dev behind qr-tools, a python library to work with QR codes, and QtQR a GUI that uses the lib and let's you create and different types of QR codes and decode QR codes easily from images, the web or your webcam. Both projects are OpenSource and mainly targeted to Ubuntu users. I haven't been actively developing them, just some maintenance. They seem to have a pretty good use base but is hard to tell with this type of projects. I've never talk about it because is not a usual conversation topic, QR codes are not use that much where I'm from and less on the desktop.