Terminal Services relies on ActiveX to run. I've never seen a client for anything other than Windows.

The web client is an ActiveX component, which can be found here:
 
http://www.microsoft.com/windows2000/downloads/recommended/TSAC/default.asp
 
and a FAQ on it can be found here:
 
http://www.microsoft.com/windows2000/techinfo/administration/terminal/tsacfaq.asp
 
Whereas the other clients are a basic Win32 setup that is usually installed with Adminpak.msi or from the server itself (remote install or floppys). Maybe you can use some emulation format to run it from one of the latter, but I wouldn't know how to do that. However, all new development is geared toward the former (TSAC) which has the ActiveX underpinnings as vital3d3 mentioned.

Thanks for your answers... I really appreciate it...

Rdesktop ( http://www.rdesktop.org/) is what you need. If you want an official client, you'll have to go with Citrix.

Wow! Thanks, Intlharvester that's what i needed...

That is pretty cool, makes me wanna try Linux again...