On Friday, 25 October 2013, FBReader for Windows Phone was removed from public access, due to information that it uses some code from a third-party non-GPL program, Fiction Book Reader. Fiction Book Reader author Vitaliy Leschenko and FBReader for Windows Phone port authors CactusSoft discussed the problem and resolved it. Parties have no claims against each other and are open for future collaboration. Vitaliy's code is still present in FBReader for Windows Phone sources, but now it is licensed under the GPL.
FBReader is available from Windows Phone Store again. Sources will be published again after making corresponding changes in author names in comments.
FBReader.ORG Limited role was just that of an observer. We are pleased that the conflict ended so quickly and peacefully.
FBReader on Windows Phone Store
Vitaliy Leschenko's blog
FBReader page on CactusSoft site