The #dos channel is on EFnet, the standard IRC network. It is also on Idealnet (run by the same operators). Some servers that worked for Marc Williams are:
EFnet Servers
Primenet (AZ)
Voicenet (PA)
Cris (MI)
UCI (CA)
Anarchy (TX A&M)
AIS (IL)
Digex (MD)
Pheonix (TX)
Becker1
Frontier net
Ionet
MO net
Concentric net
Voyager Online
Toronto, Canada
Sudbury, Canada
DALnet Servers
Spider (CA)
Voyager (CA)
Dragon (NE)
Idealnet Servers
AASP (MA)
Intrepid
BigWorld
POV (TN)
Icenet Servers
Linking Server. Type /links for servers
Slurpee (CA)
Frozen (MO)
DockerNet (WI)
IRCnet
AimNet
Openface, Canada
Stealth, NY
Webbernet
IGCOM
South Africa (link to NY)
FEFnet
Main FEFnet Server
LIII (NY)
VillageNet (NY)
Blizzard
STF
Vendetta
SorceryNet
Mordor (TX)
Kechara (MA)
Deathstar (PA)
World Wide Free-Net
A.F.N. Free-Net
PrairieNet (IL)
GRFN
TrueNET
GoldRush, CA (local?)
Erols
QNet/Queer Net
Eugene, OR
St. Cloud, MN
LinuxNet
AccessUS
LAME Communications
Wisp
BSDNet
FreeBSD.ORG
INNA
Local (non-network) Servers
MIT (MA)
Austin (TX)
Epix ()PA
South Africa