That article is ancient and might not be applicable any more.
The official instructions:
https://justgetflux.com/linux.html They're from 2011 instead of 2009, but possibly outdated as well.
Look through here as well. Should be your first stop for any Ubuntu issues anyway. Pay attention to what version they're talking about. 14.04 is the most recent and I suspect that's what you have?
http://askubuntu.com/search?q=f.lux
If you can't find a solution in the end I would suggest Redshift instead. Does the same thing as Flux. it should be in the official repositories, so just open Synaptic or the Software Centre and search for it or just type "sudo apt-get install redshift" into a terminal.