zquake/fuhquake/ezquake are focussed on usability in real-world competitions e.g. nqr, duelmania etc.
fte/darkplaces/tenebrae are generally focussed on providing a showcase for their respective authors' talents at programming graphical effects and including large numbers of features
you got tenebrae right, except that tenebrae is not focused on large numbers of features, just pretty ones.
FTE is not a showcase of programmer's abilities. It is an engine targeted towards casual gamers. The sort that would never play a game simply because it looks like it's 5 years old. :p
Darkplaces is aimed primarily as a modder's engine, although I personally consider FTE to be more modable anyway.
The real reason that fte does not have all these teamplay oriented features is because I personally consider them to be cheats. They are also relativly easy to implement and I simply have no personal interest in them, what with me not being a real gamer. I started FTE to give me greater experience of programming. It has a vast range of features because those are the features that are technically interesting, amusing, or minor stepping stones to the next big thing. Typically I do all the complex stuff, and TimeServ comes along and does all the user-based stuff. However, he's not a real gamer either.
If you're reading this, are a reasonably competent coder and an avid quakeworld player, feel free to volenteer and we'll try and find something fitting your general level of ability and interests. FTE needs YOU!
Xtife: FTE considers realtime _world_ lighting as a cheat, because you can place lots of lights in strategic places in order to see the shadows of players as they come around corners. Realtime lights on rockets and explosions and stuff are not cheats. Only predefined light sources are cheats.
world realtime lights are always going to be too slow to be really practical in a competition, so the fact that these are considered cheats is really a moot point.
bumpmapping, specular, and shadows on rockets are not cheats.