Currently MetaFrame XP is up to Service Pack 2 / Feature Release 2. You can check this by right clicking any server in the CMC and choosing Information. This should also show all hotfixes applied.
If you have Feature Release 2 licenses (available via Subscription Advantage only), then you just need to activate these.
If you do not, then when you install the software, you will have just applied Service Pack 2, and no further licensing activation is necessary or available.
Hope this helps CitrixEngineer@yahoo.co.uk