No, it does not void your warranty as no jailbreak is needed and as it doesn’t go against Apple’s security, they cannot void your warranty for using it. It is used the same way as any other official app, and it is reliable, safe, and secure to use.
The only time you may need to be wary is if you download any of the apps – if your device has to go in for repair, simply remove the tweak and reinstall it later.