Check this out
My interpretation is that you do not need a separate license if the OHS is installed on the same server as the database, but if it is installed on a separate server, then it needs to be licensed. As you are licensed for OHS through OBIEE, then you should be OK. As I said, that is my interpretation, but if you are unsure, you should check with Oracle.
Thanks guys, I think we can use "APEX Listener " as OBIEE comes with Weblogic server also.
I'll check with Oracle team about licencing.
That would be better, as the Apex Listener appears to be Oracle's preferred architecture.