My question was raised after I read the BIFAQ, where it is stated:
<i><b>Which BW 3.5 front-end versions can I use on top of NetWeaver BI 2004s?</b>
You can use SAP GUI 6.20 with the latest BW 3.5 front-end patch to work with an SAP NetWeaver 2004s System (only BW 3.5 front-end functionality).
You can also use SAP GUI 6.40 Comp 4 or higher and BW 3.5 front-end ('BW Add-in') (only BW 3.5 front-end functionality).
SAP NetWeaver 2004s BI front-end is installed separately ('BI Add-in' on the installation CD).
<b><u>Is the BW 3.5 frontend (with GUI 6.20) identical to the BW 3.5 frontend add-on (with GUI 6.40)?</u></b>