OSE for Office Xp

I want to setup a Discussion Server on a Windows 2000 Server. To do this for
Office 2000 all that was required was to install Office Server Extensions
which was shipped with various version of Office 2000 on the IIS server and
it could be installed on the server so long as there was a license for that
version of Office for the server on which it was being installed

My question is what is the equivelant of OSE for Office XP (i.e.what do I
need to setup a discussion server for office XP). Whatever the solution is
do I require a separate license of the client and server side of the tool.

Thanks is advance

...pc