To fix the blurred screen in desktop sharing, you have to manually recompile the openmeetings source file

org\openmeetings\webstart\screen\CaptureScreen.java 
There are two lines in public byte[] bufferImage():
double thumbWidth = 600;
double thumbHeight = 600;

Which limit the maximum height and width of transferred image. Afterthat, you should update your screenviewer.jar inside openfire/plugins/red5/screen and all should be working. I walked through some huge maze to get that answer