If by Terminal Server you mean a Windows terminal server then yes, the client is installed by default on the device.
As for AS/400 access, Skofarrel has it right, there are some clients, like the one he mentioned:
http://www.msmobiles.com/news.php/1902.html
There is also a port of PuTTy for the PocketPC:
http://pocketputty.duxy.net/ in case you need SSH.