Not sure where to post this, but I just found this amazing program:

https://sites.google.com/site/ccdsurgeon/

"Insane Bump runs on OpenGL and is cross platform and runs on both linux and windows, macos is planned."

I have been using Gimp's InsaneBump-plugin, but for some reason the preview doesnt work on the resent version in Linux, so I thought someone else might find this usefull.