Thanks for sharing Chriztofr!
Patchou, to create a test server, I'd recommend downloading a free copy of VirtualPC from Microsoft and setting it up in that.
This is a basic step through of how I'd imagine setting up communications server/communicator would go:
1) Install Windows 2003 Server
2) Select that you want to install Active Directory, go through prompts, remember what you put for domain name
3) Control Panel > Advanced > Users and Computers
4) New User (username) x however many
5) Install Communcations Server
6) Install Communicator (client), log in with username@domainname
Patchou/Chriztofr, are either of you looking at implementing live spell checking (either for standard MsgPlus or for the Communicator addon)? If you want to see a best-case implementation, look at Gaim/Pidgin which uses aSpell, a free library.
There's already a very basic script for MsgPlus which gives a very basic level of spell checking but it doesn't check as you type and it doesn't give suggestions, it just auto-guesses for anything it can't recognise. Plus you need to mark each message you want checked.
http://www.msgpluslive.net/scripts/view/292-aSpellChecker/