During today's Quake Con keynote the id folks announced that they have a team of developers working on a little pet project called Quake Zero.
QZ will be a free web-based version of Quake 3 multiplayer. Todd Hollenshead told me they decided to kick off this project for several reasons. First and foremost, id hated to see their game, once quite popular for online matches, losing its prominence in the online gaming scene, this will allow virtually anyone with a computer to play matches of their games.
Hollenshead said id also wanted to dip their toe in in-game advertising, and that this seemed like the best way to approach it. So expect ads to be running on the web page when you play Quake Zero,but free games for ads seem absolutely fine to me.