I have set up a new csDoom master server (csdoom.voxelsoft.com), as the original csdoom.dhs.org seems to be down again.
Current master's server list can be accesed at:
http://www.voxelsoft.com/csdoom
Any server ops are welcome to use this master server as primary or backup. I've also hexedited a copy of the original launcher to use this master.
http://www.voxelsoft.com/csdoom/launcher2.zip
I may be releasing a new client soon.