Gonna need more info on the server to answer your question. Is it a LAN only?

No it is not a "LAN-server", it is supposed to run over the internet with a password but when I checked it's console (about five minutes ago) it said

"Connecting to list server...
Failed to make connection to list server...".

I have opened ports 2202 - 2400 but it won't work, I have also given the program (FLServer.exe) full access to the internet (software firewall, ZoneAlarm).

You say you messed with flserver but that had to be on your friend's 'puter, right? Opening the ports is needed only for his server, not for your client.

If his server is not being seen on the FL global server list then the problem is at his end. What does the flserver console messages say? It should have the following to show it logged into the FL global list server. <pre><font size=1 face=Courier>Server running, ready for log in.
Connecting to list server...
Established connection to list server...
Sending game information to list server... </font></pre>If this isn't the problem then you may have the wrong port client-side. Even so you should be able to log in through the list from the FL global list server.

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Earendil
SysAdmin of Boston Freelancer server
Server community website & forum: EarendilsPlace.net (server rules)

Thanks for the help!
I figured it out. The error message in FLserver.exe's console was caused by a corrupt AppGUID in freelancer.ini. I just got him a fresh one and it worked!