Why is the Gimp website so useless. I wanted to see if they still have the strange UI with floating windows but couldn't find a screenshot of the actual software on the site.
You can run GIMP in either single window or multiple windows mode, there is a setting in the "Windows" menu that switched between the two. The multiple windows mode is the default and IMO works better if you are using a window maanager with a virtual desktop dedicated to it (or graphics apps in general). In my Window Maker-based setup i have a virtual desktop for graphics apps and i have it configured to always place GIMP windows in that virtual desktop. The main thing i'd like is being able to preserve the tear-off menus across launches (GIMP remembers the various window locations but always closes any persistent menu windows).
You can find screenshots on the tutorial pages: https://www.gimp.org/tutorials/