Edit the WebLogic registry.xml file to convert it to a Weblogic 7.0 file.
after that you're able to use Weblogic 8.1 from within JBuilder 8.

<?xml version="1.0" encoding="UTF-8"?>
< bea-product-information >
    <host home="C:\bea" name="Server_Name" number="1">
        <product format="1.0" name="WebLogic Platform">
            <release BeaProgramGroup="BEA WebLogic Platform 8.1" BuiltInServicePackLevel="0" InstallDir="C:\bea\weblogic81" InstallTime="Nov 11, 2002 9:28:57 AM" JavaHome="C:\bea\jrockit81_141_02" JavaVersion="1.4.1_02" PatchLevel="0" ServicePackLevel="0" Status="uninstalled" level="7.0">
            < /release >
        < /product >
    < /host >
< /bea-product-information >


Now if only we could replace the EJBC compiler with the new and much faster appc,  but EJBC still works.