I got the Tethealla Server from sodaboy's site and am trying to setup a server for myself.
Sadly sodaboy's forum is gone and I don't know where else to go.

I followed the instructions and got to the part when I just need to login.
Whenever I run PsoBB_Localhost.exe or PsoBB.exe, they simply crash.
Can anyone tell me how to get it to run?
Thanks!

Have the game installed and throw the localhost exe into the directory of the client install and run it from there.

That
A) gets me a 903 error
B) is pointless because I cannot edit drops or exp gain

Err...
That file is client sided and has absolutely nothing to do with the server configuration... (else anyone could edit their exp and drops on any server) Those files should NOT be in the same directory as your server. psobb_localhost.exe still needs to be able to read all the models/textures/text/music/sound files, so it needs to be in the same directory as them (or rather in the parent directory where the /data folder resides)

Ensure your 3 server exes are running and that you've opened your ports. If it still doesn't work, recheck your tethealla.ini and your ship.ini and restart your servers.
If it still doesn't work, your router may just suck.

@Choko if you talk with Soda i don't mind hosting the old forum etc keeping it closed.

I'm not really in contact with him either though. ^^

YES!
IT WORKS!

Thank you so much!

Do you guys maybe got an old client lying around?
And does anyone know how I can turn on all quests, so that I don't have to unlock ever later tier in every difficulty?

Why would you need an old client? What do you want on it that you don't have on the localhost one?

You'd need to edit the code that checks to see which ones you've completed and which ones should be available to you (just make it make all of them available)

The current client insta-kicks on god/equip and other hacks, using a tech not for your class and doesn't work with spof either (it has a feature to randomly add NPCs hunters to your party among other stuff).

Also, where can I edit the code that checks which quests I completed?
Can't be in the script of the actual quest I want unlocked because I can't get there in the first place.
I tried to look for a global variable that is set when you finish all tier 4 quests (assuming it works by lower tier quests setting variables that the server reads at some point in some place I don't know), but I couldn't find anything like that.

That isn't the client, that is the server that is kicking for that stuff xD
To disable the kicks for that, search for the message that you are getting when you are disconnected and comment out the if statements and client->todc = 1; lines (may need to refactor a bit if he used an else statement to continue for some reason)

if you want all quests to always show just change all instances of
show_quest = 0;
to
show_quest = 1;

if you want to change the rules of how they are displayed, edit the qflag functions (I think there are two right next to each other if I can remember)

EDIT: for spof it is configured to scht's server (it is outdaded though) so it won't work on your server unless you update spof to do so. I'll leave that one to you to figure out though ^^