You can download the Weblogic Server 6.1 here:
http://commerce.bea.com/downloads/weblogic_server.jsp
You can get the one that supports J2EE 1.2 Plus J2EE 1.3 features. You can also request a CD if for some reason, you're unable to download.
There's also resources for BEA developers at: http://dev2dev.bea.com
Hope this helps.