There is at least one or two other Java Quake 2 projects out there from a few years back
http://www.planetquake.com/q2java/ for one. But the real gold was a Java Quake 1 client done back in 1997 which is amazing because Quake was still new. IT was called JQuake
http://hem.passagen.se/carebear/JQuake.htm
It ran in a small web browser window. But ID got to them and told them to shutdown. Then they redid everything with their own graphics instead of ID's and came back as Frag Island which is still there but is missing a couple of key files somehow so it hasn't run it years. Even John Romero was impressed and wrote them a letter complimenting them while nicely asking them to shut down if I remember right. I have some of the Frag Island files but I wish I could get a hold of the original JQuake. I heard those guys are MIA even though the site is still there though broken.