As you may know, GIMP is an open-source photo manipulation software, being a good alternative to Adobe Photoshop.
The latest, under development, version of the software is GIMP 2.9.3 Git, which is already usable.
Up to date packages are available via Otto’s PPA, so installing the software on Ubuntu 15.10 Wily Werewolf, Ubuntu 14.04 Trusty Tahr, Linux Mint 17.x and Elementary OS 0.3 Freya systems should not cause too many problems.
All you need to do is add the PPA to your system, update the local repository index and install the gimp package:
$ sudo add-apt-repository ppa:otto-kesselgulasch/gimp-edge
$ sudo apt-get update
$ sudo apt-get install gimp
Optional, to remove gimp, do:
$ sudo apt-get remove gimp