Today I've noticed that doom.com.hr Competition Doom server was v2.0.2... so now it's fixed and you can use it for cooperative / deathmatch / whatever games.
All you have to do is add -connect doom.com.hr or enter it in Competition Doom launcher.
ps. hehe, I forgot that cooperative is not implemented in Competition Doom. You can record demos but they will not be valid so I will not bother with database/upload. It's just too much work. Sorry