Yes - If you view the requirements under Sametime Conference, you will see more complete information. We are working to get this data updated. The minimum supported level is WAS 8.5.5.8.
http://www-01.ibm.com/support/docview.wss?rs=477&uid=swg27007792
Click Sametime 9.0.1 Conference, then Prerequisites. The WAS prerequisite is the same for all varieties of Sametime 9.0.1.