It's still alive, to some extent. Priit Kasesalu (of Skyroads, Kazaa and Skype fame) wrote an alternative client back in 2001: Continuum. Some of the bigger servers (EG, TW) are still around. Many of the smaller ones like SFSS have long since perished.
The netcode in subspace was a bit better, probably due to needing to deal with 200ms+ pings that were common back in that era.