We are considering releasing a version of FBReader that would have support for a DRMed e-book format and this version most likely will be released under a license different from GPL. Since so far FBReader was released under GPL only, it either included or relied on code that was under GPL compatible licenses. We are going to re-implement all such code so it could be licensed under a different license.
Unfortunately it means that all patches you send to us should be allowed to be re-distributed under both GPL and a proprietary license. If we are not allowed to do that, we won't be able to accept the patch.
We'd like to emphasize that we have no plans to stop releasing FBReader under GPL: we are going to release all code that we can under GPL (currently it means all code that is not related to DRM).