[1] Download the binary from here (I don't know/care where in ubuntu/debian repository it can be found):
http://ubuntu-ky.ubuntuforums.org/showthread.php?p=6930123
[2.1] Gnome: just copy the files from extracted "Flurry" directory in /usr/. I wrote a little script to make it easier.
##########################################################
#!/bin/bash
tar_file="Flurry.tar"
#extract
rm -rf Flurry
tar xvf "$tar_file"
#copy files
cp -u -v Flurry/usr/lib/xscreensaver/flurry /usr/lib/xscreensaver/
cp -u -v Flurry/usr/share/xscreensaver/config/flurry.xml
/usr/share/xscreensaver/config/
cp -u -v Flurry/usr/share/applications/screensavers/flurry.desktop
/usr/share/applications/screensavers/
##########################################################
[2.2] KDE: copy the files in /usr/ and create
"/usr/share/applnk/System/ScreenSavers/flurry.desktop" with the following content. It will put flurry in the KDE screensaver configuration menu and let you set the options:
[Desktop Entry]
Encoding=UTF-8
Exec=flurry
Icon=kscreensaver
Type=Application
TryExec=xscreensaver
Actions=InWindow;Root;Setup;
X-KDE-Category=OpenGL Screen Savers
X-KDE-Type=OpenGL
Name=Flurry (GL)
[Desktop Action Setup]
Exec=kxsconfig flurry
Name=Setup...
Icon=kscreensaver
[Desktop Action InWindow]
Exec=kxsrun flurry -- -window-id %w
Name=Display in Specified Window
NoDisplay=true
[Desktop Action Root]
Exec=kxsrun flurry -- -root
Name=Display in Root Window
NoDisplay=true