Fluidity is GTD software for "black belts", or those aspiring to that level.
I wrote it for my own use, but maybe it can help you, too.  (And if it does, 
I would really like to hear from you.)


****** ############  VERY IMPORTANT - DO NOT IGNORE!!  ############

Fluidity is currently a BETA release!  I have not personally had 
any data loss problems in using Fluidity for over 3 years, but that doesn't mean
there aren't any data-destroying bugs hiding somewhere.  Don't sweat it too 
hard - your data files get backed up to ~/.local/share/fluidity/backups/ 
so if you do regular backups of your home folder, you'll be fine.

(If you don't currently do regular backups, I recommend CrashPlan* or Deja Dup)

* http://crashplan.com -- full disclosure: I work for Code 42 Software, 
  the makers of CrashPlan
******

Now on to less unpleasant things...

INSTALLATION
See the file "INSTALL" -- includes system requirements 


RUNNING THE APP:
From an install: Look in your GNOME/KDE menus under "Office"
From source archive extract: just run 'launch_fluidity'

Also, try out Fluidity Slider - it's a tool for ultra-fast input of new inbox 
notes and next actions.  The notes you input into Slider will automatically
show up in Fluidity's "Stuff" list in the Clarify section.  Slider is available
by either clicking "Add Stuff" in the Clarify section, or by launching it 
directly -- it's in bin/slider.  (If you end up using Fluidity for any length of
time, I highly recommend binding it to a global hotkey on your desktop.)


FINAL NOTES:
Finally, try not to laugh at my weak hack-fu and I'll try not to laugh 
at your (possibly) weak GTD-fu. ;-)