John Carmack has announced that Quake III Arena will be Open Source by the end of this year. In a reply on a Slashdot thread he said the following:

Re: Quake3 engine open-source? When?

by John Carmack (101025) on Wednesday August 04, @03:13AM (#9876519)
By the end of the year. There are still a lot of higher priority things, but it is coming soon.

Hopefully punkbuster will keep the source release from having any negative impact on the player community.

John Carmack
slashdot post

[hide=And about Doom 3 he says..]
I'm proud of it. (Score:5, Informative)
by John Carmack (101025) on Wednesday August 04, @03:56AM (#9876672)
I am extremely proud of Doom 3. I think it is the best game we have ever made, and it exceeded all of my expectations. That is a rather trite phrase, but it is literally true -- I had a good set of expectations for how the game would turn out based on the technologies that it was built on, and it wound up being just plain better than that.

We think a lot of people will like it.

I don't follow gaming message boards, because, at its best, entertainment is going to be a subjective thing that can't win for everyone, while at worst, a particular game just becomes a random symbol for petty tribal behavior. This slashdot story is about as close as I want to go...

Amidst all the various Doom ports and expansions, we are starting up on our next game. It will have a new rendering engine, which will be keeping me busy for a while, but the only other thing we are saying for now is that it won't be a sequel to any of our previous work. We have a really solid team that did a lot of maturing through Doom's development, so I have high hopes that it won't be another four year odyssey.

John Carmack
slashdot post