I'm testing klik on a gentoo-box and it works like a charm in the few cases I've tested yet - except for gimp:
After mounting the image, /tmp/app/1 permissions were set to 700 and the owner was the user with ID 1000 who doesn't exist on my system (root had no problem to use the application btw).

In order to fix this, I tried to remount the image rw, but that failed even after setting the permission of gimp_2.0.6.cmg to 777.
The error message was always that the filesystem would be mounted read-only despite what I wanted.

Though I left a small message on the website with the gimp-download to give the developer a chance fix this, I'd rather know how to fix this myself, because I think it's better to give a step-by-step explanation how to fix a problem than just telling the developer to fix it.

cu, tom