It's a common rule that for all Teamwarfare.com games that a HUD modification is not considered cheating. The reason for this is because once you begin saying certain HUD modifications are illegal, you ban them all and everyone's game has to look the same with specific settings. Some people, such as myself, have poor edge detection in the dark which is why I always have to max out the gamma in the games I play. Some people would consider my increasing my gamma to that level cheating however if it weren't for that modification, I wouldn't play trem.
In reality, it should be standard on everyone's install; tis pointless not to do it.