From what I've read on other sites, Gimp does not work or partially doesn't work.
What is known is that MacOSX Leopard came with a lot of changes.
One of the changes was to the Unix core of OS X.
Leopard is the first Mac OS to receive a full on Unix certification, and in order to do that Apple had to change a lot of the ways that Unix interacted with the OS.
That's why the problems you describe exist.
And if I may quote you:
Hey all guys, I am having a trouble in my Mac, leopard 10.5.8. Ever since I updated to 10.5.8, my native made apps meaning X11 apps which were ported natively like Gimp are not working. The GimpPainter or Gimp.app bounces in the dock and stops like other apps but doesn't load, I don't see no window or loading signs like gimp.app is not working. Am I the only guy having this trouble, as i have searched about it in google. Please if you have any ideas please help me.
In my opinion if an App bounces and doesn't open, it more or less doesn't work, does it.
If my directions to Aqua Gimp helped you, I'm glad... If you're asking me to solve you're problem with the native Gimp, I'm afraid that's a bit out of my league as well.
Good luck