id Software has fixed the masterserver after weeks for Quake III / Team Arena, Return to Castle Wolfenstein, Wolfenstein: Enemy Territory.

Server support for Quake III/Q3:TA, RTCW and Wolf:ET are back online! Thanks for your patience (id Software Twitter)

The Wolfenstein: Enemy Territory Master Server (along with the other idTech 3 masters) is back up and running. Thanks @idSoftware! (Splash Damage Twitter)

In the time without the masterserver the community had created a fix for Wolf ET, see etmaster.net and Splash Damage forum.