When it comes to Ubuntu versions such as 10.10 Maverik, 10.04 Lucid, 9.10 Karmic, 9.04 Jaunty, 8.10 Intrepid, 8.04 Hardy, etc, people often will try to install packages from say Ubuntu 10.10 Maverik on an Ubuntu 10.04 Lucid desktop. Unfortunately, this may not work.
To better explain the reason, one needs to understand how Linux software works. If we take a look at GIMP-2.6.8, we will see that it needs several programs installed first. These programs are:
These programs are what we call dependencies. GIMP depends on these packages to work. Therefore, without these packages, GIMP may not work correctly if at all.
So, when it comes to installing GIMP-2.6.8 on Ubuntu 10.04 or an earlier version, that is if that version of Ubuntu uses an earlier version of GIMP, one needs to first check if the dependencies are met. If the older Ubuntu version uses fontconfig-2.7.0, which I assume is an older version of fontconfig, then GIMP-2.6.8 may not work correctly or even install.
Therefore, depending on how Ubuntu set-up their installation packages in the Ubuntu repositories, the installation will either fail, will not even start, or will install, but may not work correctly due from the fact that the dependencies are not met.
In summary, it is best to just upgrade Ubuntu to the version that has the software version that you want. After all, if a newer program works 99% of the time in an older Ubuntu version, but works 99.9% of the time in the newest Ubuntu version, I would rather have it working 99.9% of the time.