Hot on the heels of the 1.4 game update comes the final version of the Enemy Territory: QUAKE Wars Software Development Kit! There are a number of improvements and fixes in this version that you can find neatly documented and formatted after clicking the "read more" link below. In addition to the SDK itself, there's also the MegaTexture Media Pack, which anyone looking to create custom MegaTextures will find incredibly useful.
The download weighs in at over 600MB but includes everything required to make custom levels, models and mods for the game.
To assist all you budding modmakers out there Infinity Ward has also created a 'Community Wiki' with documentation and tutorials to help you get started.
The Mod Tools do not work in Windows Vista, although it is reported that some people have successfully run them in Windows XP Compatibility Mode.