The problem is not specific to the Redmond theme. In fact, I couldn't find any
theme that would draw the border for normal windows, but not for maximized
windows. Laptop and CDE themes show exactly the same behavior.
The code responsible for this behavior seems to be in kdebase/kwin/client.cpp,
function Client::maximize. There is a comment "hide right and left border of
maximized windows". No word about top and bottom borders.
It seems that the generic code (i.e. not specific to any theme) doesn't know the
border width above the title bar. Maybe it should be added to the WindowWrapper
class.
Anyway, here's my patch for the Redmond theme. I have tested it, and it works
just fine for me (KDE 3.1). But I'm not really familiar with KDE code, so please
be careful.




Looking at the code for the Redmond theme
(kdebase/kwin/clients/redmond/redmond.cpp, function GalliumClient::paintEvent),
it appears that the code is not specifically trying to suppress any borders,
vertical or horizontal.

Created attachment 1134 [details]
Patch that removes borders from maximized windows

When the window is fully maximized and the maximized windows cannot be moved
(it's an option), grow the client area by 4 bytes in every direction to push
the borders out of the screen. Unlike the common code, I don't care if the
panel is bordering the window on one of the sides. Borders are annoying even
when they touch the panel.

I think the solution to this bug should be linked to the Control Center > Desktop > 
Window Behavior > Moving > "Allow moving and resizing of maximized windows" 
option. If this option is disabled then there's no reason to show the border since you 
can't resize the window anyway. If this option is enabled however the border should be 
still shown. 

The patch is wrong, sorry, you can't just push the borders out of the screen. That's also the 
reason this feature was disabled until it will be implemented properly for KDE3.2. 
 

*** This bug has been marked as a duplicate of 56654 ***