Sorry for reviving that old thread, but this is currently the first Google result for "fernflower", so I think it would be nice to post here to guide people looking for more information about this decompiler. Fernflower should get more popular now, since it is integrated in the IntelliJ IDEA version 14 IDE, which is very popular including among Android developers.
The source code posted by ostar2 was decompiled from the Fernflower binaries. The good news is that the original sourcecode is now available and under Apache license
It includes the standalone decompiler which can be used outside of the IDE:
CLASSPATH=java-decompiler.jar java org.jetbrains.java.decompiler.main.decompiler.ConsoleDecompiler