The only way I would fund GIMP is if that funding went directly towards a better UI. It's not worth improving the algorithms given how hard it is to use.
Also, can't you just position floating windows in the right place so that they look pretty much docked in-place?
Note that I don't have any OS X machines to confirm this myself, this was at a designer's mac a few weeks ago.
What do you find about Gimp that is hard to use?