I wrote the PhraseMeme Scanner app that was mentioned, and yes it is based on the ZXing library. The app has now been released to the marketplace, and more information can be found at http://PhraseMeme.com/Scanner
I also uploaded the Silverlight port of the ZXing library to http://silverlightzxing.codeplex.com/. The project includes sample code for using the library as well as a BarcodePhotoChooser XAML/CS page for displaying and choosing sample barcodes since the emulator does not support the camera. I plan on submitting bug fixes and additional code to this project so that others can also use it in their Windows Phone 7 or Silverlight applications.
