Expect it to be available via Cydia on your iPad later today, and it will work on iOS 4.2 GoldMaster if you have it already on your iPad. Otherwise this is just another reason to jailbreak your iPad if your haven't yet!
Support along with the GPL code at Paduser.
It runs very smoothly at 1024x768, even with 4.2 GoldMaster or Beta, and it looks awesome. I recommend that you download the high resolution texture files from here. The only requirement is that you need to Jailbreak your iPad.
I remember when Quake was cutting edge and you had to have a powerful machine to run it. Now it's easily running on an iPad. I guess the iPad is magical!!!