Here are some more generic directions for setting up another client (the specific client I am giving directions for is Adium 1.4.3 as that's what I use, but it can be applied to similar clients such as Pidgin which is available for Windows and Linux, or iChat), since the Spark client is really not that great in my opinion. Any client that supports Jabber/XMPP can be used:
1. Go to the menu Adium > Preferences, switch to the Accounts tab
2. Press the + button and select Jabber from the list of account types
3. In "Jabber ID" enter "yourname@outpost2.net" (replace yourname with some kind of username that you want to use, if you already have an account use that one).
4. In "Password" enter a password.
If you already have an account skip to step 6 below, otherwise keep reading:
5. Press Register New Account. In the window that pops up, type outpost2.net into the Server field and press Request New Account. Another window should pop up asking for a username, full name, email address, and password. Username should be the part before the @ sign in the Jabber ID field on the previous screen. Full name does not need to be your real name (and probably shouldn't if you are concerned about privacy). Press OK and your account should get set up.
6. You may wish to go to the personal tab and set your alias to be something reasonable (by default Adium will use your Mac account information which may be undesirable if you use your full name or an icon of you for your account) if you are concerned about privacy. Similarly, on the options tab you may wish to change the contents of the resource field (it defaults to your computer name which in my case was "<my full name>'s-MacBook-Pro" and people can see this if they add you as a contact).
7. Press OK to create the account, and let it connect. (You may see warnings about a certificate error since we don't have a real SSL certificate; this is ok and you can ignore this. I ended up adding the certificate to my keychain to prevent it from complaining).
8. Go to File > Join Group Chat, enter "outpost2" into the chat room name, the rest of the settings can be left at defaults (you may wish to change the handle if you didn't change the alias information above). Press Join and you should see a chat window pop up.
You may wish to add the resulting chat room as a contact for easy access in your contact list when you start Adium in the future.
Happy chatting!
There is one other thing that may be of interest to people who use other XMPP services such as Google Talk. Server-to-server federation should be working which should allow you to chat with other contacts on different XMPP servers, if you use their full username@server when creating the contact. It worked for me with Google Talk, I did have problems with another 3rd party server but it may have been that server's configuration (ours is correct as far as I can tell to allow federation to work).
-- BlackBox