WMS in 2008 for custom use + license

[Benoit]

Hi all,

I'd like to develop a silverlight application connection to a windows
media server (Windows Server 2008 web).
I would like to develop a services based on 'play until you stop
paying'.
I would like the client to be silverlight based and the server based
on a mix of .Net aspx application and windows media services.
I imagine that when a customer buy a 'weekend pass', he get access to
the service for a limited time and he can download (or stream?)
medias.
I would like to use the DRM to be able to deny access to media once
the pass is over.

Do you know if Windows Media Services is what I need ?

Which licenses do I have to get to use all theses features?

Thank you in advance,

Bp