Remember a year ago or so when we had some coop servers running? Most of them got lost in the process when
Jollen.se servers went down and there hasn't been a new home to them... yet.
Few days ago
Qqshka added support for cooperative game mode in KTX so you can actually play the normal single player campaign in KTX server if you wish to. The command for this is:/votecoop
And it also disables cooperative game mode once you're finished with it. I'm sure there are some bugs left in the code (like players telefragging each other after map change etc) but feel free to test this, you can find servers that support coop from:
Report any bugs/feature requests here.