The GIMP

The GIMP (GNU Image Manipulation Program), available at [www.gimp.org]

You should find a version for almost any platform. (And its Free)

Terrain Maps for UT2003

Generating a terrain map for UT2003 is pretty simple in The GIMP.

A few quick easy steps to have a nice random terrain map.

Create a New image.
Right click in image goto filters → render → Clounds → Plasma2
Tweak settings to your pleasure and hit "OK"
Right click in image goto filters → Blur → Blur
Run it 30-50 times depending on how smooth you want the terrain. (Theres a repeat # of times option)
Tweak till you have what you want.
save as bitmap.

And your done.

This seems to generate terrain that is a bit "bumpy" in spots but running the in-editor smooth over it seems to work wonders.

Creating a seamlessly tiling texture in GIMP

Size your intended image to what is appropriate
Go to Layers>Transorm>Offset
There is a choice to simply offset by half in both x and y, or you can enter your own values if you prefer
Now you will see lines in the image, these are your old edges
Press the "c" key to bring up the cloning tool
Sample an area with a brush ( holding ctrl while left clicking) that has about 95 per cent hardness, I will typically start with a brush that has a diameter 1/4 the width and or height of my texture then use a small one for finishing touches
Once you have gotten rid of the lines, offset the image by half again to check and make sure you didn't create any new edge discrepancies, if it looks good, offset it again and save it for import into UED

Useful UnrealEngine-related plugins

The following two plugins help provide the same features as nVidia's texture tools, without the need for Photoshop:

[DXT-compressed DDS support] (Note: use "Save As" to get at the properties and set the compression; UnrealEd seems to barf on uncompressed DDS files)
[Normal map generation] (for UnrealEngine 3)

But how do I install the damn thing?

Debian

On the console, type: apt-get install gimp

For RedHat, Mandrake, Suse

(and other RPM based Linux distributions): If you selected The GIMP while installing the distribution, it's probably already installed. If not, use the software manager or package manager of your distribution to install it (or if you prefer the console, use rpm).

For Gentoo

On the console, type emerge -av gimp, or use a graphical tool if you'd rather (kportage, porthole, etc.).

Windows

[Download installer here]
The official homepage is [here]; seperate packages of precompiled dependencies can be found here too.

Mac OS X

[GIMP.app].

Everything else

Try compiling the sources which can be downloaded from http://www.gimp.org or check your distribution's package management system if it has one