Hi Reynir,
the Netweaver portal that comes with the BI-JAVA installation is needed as "runtime" for the Design Studio Applications. Same as for the 7.x Bex Web Applications.
If you can run 7.x Bex Web Applications you must have the portal even if you do not "see" it because it might be that the typical portal navigation is hidden.
So I would guess you have everything you need already.
Regards
Dirk