Ok, I've nabbed the new Beta developer tools for Windows Phone 7 (and still cursing the fact that no offline installer is available) dropped it into a test VHD and did a quick test project to test out wheter the previous Silverlight 4 port of the library works on the phone (and also in Silverlight 3) and... well.. it works without a hitch, so if you were looking for a QRCode library for use in  Windows Phone 7.

Download it here.

Enjoy!