This QuakeWorld-based engine powered some of the most critically acclaimed engine's of it's day, like Half-Life, Counter-Strike, Day of Defeat, and many more.
Great engine! Really good for modding. Half-Life modding is done with a real programming language, C++, not a wimpy script! Pffft! Let's see a total conversion flight simulator done in UnrealScript! You can do anything in Half-Life, whereas you're limited in other engines by scripting languages. Sure, the learning curve is a bit steeper, but the possibilities are limitless.
One of the best engines. Created for the modding, he gave an amount of famous games as Counter-Strike, Day of Defeat and Team Fortress.
Today, unfortunatly, his community and content is still unknown, because scattered in a lot of small websites. I think we should creat a facebook group to gather this community. The content can be upload on ModDB, on a wiki, and a lot of other things. It just has to be good organized.
And a lot of other websites.