"Domino 8 is 100% Domino - no 'ifs' or 'buts'. It will run all yourexisting Domino applications and email. It is a regular in-lineupgrade from earlier releases - no rip-and-replace of servers isrequired. Domino 8 has no hidden prerequisites or new requirements foryou to install (IBM WebSphere Application Server, IBM WebSphere PortalServer, and IBM DB2 are all optional extras you can chose to deploy).Nor does it require that you deploy any of our collaboration productssuch as Lotus Sametime, Lotus Quickplace, or Activities. We willcontinue to integrate well with these products to add value to yourcomplete collaborative application environment."
Certainly, if you want more capability, such as Sametime, you'll have to have a Sametime server. That seems obvious to me. Activities does require WAS to run, but that IS optional. Besides, Activities is basically a pure Web 2.0 app that can be used in lots of different contexts, both with Notes and standalone.
Domino 8, What's New
Manager, Product Design