1up has updated the following servers with the recently released 4.1
.1 Urban Terror zpak00_1:
1up Jump Server
1up Icy Jumps Server
1up Christmas TDM Server
Information about this update is available at the
Urban Terror Forum.
Is 4.1.1 required on clientside to play on the servers?
No, the 4.1.1 update is not required to play on any 1up public server.
[1] To sum it up:
1) If you have Urban Terror 4.1 and you connect to a 1up server you will be able to play the game as always.
2) If you have the Urban Terror 4.1.1 update you will still see the 4.1 content in all 1up servers with the exception of the Christmas and two jump servers.