It also seems to work for versions 8 and 9.  

 (JBuilder version 6 and 7 have installers for Mac OS X, so you should use those.)

 Steps:

 1. insert the JBuilder CD

 2. in a terminal window, change directories/folders  to the following directory: 

       /Volumes/<name of jbuilder 9 cd>/Solaris

   you can also use the Linux distribution.

 3. run the following command, assuming you have the Enterprise version:

      sh ./ent_install.bin LAX_VM /usr/bin/java 

 If you have the Personal version, that would be 

      sh ./per_install.bin LAX_VM /usr/bin/java 

 Notes: 

 1. The installer hung when I tried to choose a different
 directory to install in rather than the default. 
 
 2. After starting the installer again and using the default 
 installation location the installer actually put the installation in 

    /Developer/Applications/JBuilder9

 This is the preferred location for a JBuilder installation, so 
 you should just go with the preferred location.  That is, 
 don't touch that "Choose" button!

 Once you are done installing, you have two choices for 
 launching JBuilder 8 or 9.  

 1. You could modify the app bundle, JBuilder.app, inside 
 the /Developer/Applications/JBuilder<8 or 9>
 folder.  Because this is a lengthy and potentially complicated 
 procedure, it is recommended that you forego this approach, 
 and adopt the next one.
 
 2. Use the shell script which has been published in the 
 "borland.public.jbuilder.macintosh" newsgroup.  For 
 discussions related to the script, please search
 the archives at http://www.tamaracka.com using the 
 following keywords: 

  ^jbuilder ^macintosh shell script 

 The following is a shell script for JBuilder 8.
 By saving it to a file named JBuilder8.command in 
 your Home folder, you can double-click on it to 
 launch.  You can also drag it to the Dock.  

 Modify the script for your version of JBuilder and
 installation paths.  
 
 *** begin snip after this line ***
 #!/bin/sh
 
 # Credits:
 # Original author -- Dave Yost
 # Modifications -- Paul Furbacher
 # Use at your own risk; make modifications according to 
 # your installation.
 
 # Optional arguments in the last line of this script:
 #
 # -info  prints out info equivalent to that found in the About
 #        box > Info tab.
 #
 # -verbose  prints out a verbose record of the OpenTool initializatin
 #        and more
 #
 # -license  starts the License Manager
 #
 
 echo "Environment"
 
 /usr/bin/env
 
 echo ""
 
 if [ $# -eq 0 ]
   then args="-info"
   else args=$@
 fi
 
 echo $args
 
 JBUILDER_HOME=/Developer/Applications/JBuilder8
 jdk=1.4.1
 
 useGrowBox=true
 
 cd $JBUILDER_HOME/JBuilder.framework/bin
 
 #jars=`find ../patch ../lib ../lib/ext -name \*.jar | tr '\012' : `
 jars=`find ../lib -name \*.jar | tr '\012' : `
 
 exec 
 /System/Library/Frameworks/JavaVM.framework/Versions/$jdk/Commands/java \
  -Xdock:name="JBuilder 8":icon=$JBUILDER_HOME/JBuilder.app/Contents/Resources/JBuilder.icns \
  -Xmaxf0.2 \
  -Xminf0.2 \
  -Dapple.laf.useScreenMenuBar=true \
  -Dapple.awt.showGrowBox=$useGrowBox \
  -Xverify:none \
  -Xbootclasspath/p:../lib/lawt.jar:../lib/lawt.jar:../lib/TabbedPaneFix.jar:../lib/SequencedEventFix.jar:../lib/JarManifestFix.jar:/System/Library/Java/Extensions/MRJToolkit.jar   \
  -Xms32m \
  -Xmx256m \
  -cp ${jars}:/System/Library/Java \
  com.borland.jbuilder.JBuilder $args 
  
 *** end snip above this line ***
 
 Notes on creating, editing and saving the shell
 script: 
 
 1. save file with Unix line endings, generic text file, etc.
 
 2. chmod +x filename_goes_here
 
    - Do step 2 in a Terminal window.
 
 3. save the file with a .command and it will be double-clickable
 _if_ it was not saved so that the editor puts its creator and
 filetype signatures on the file.  For example, in BBEdit, make
 sure it is saved as a "generic text file" in the "Options" 
 dialog off the "Save as" dialog.
 
 4. Note the -Xbootclasspath line may have been wrapped by 
 your newsreader.  The lengthy "exec ..." command may be 
 broken across many lines, but each line must end with a 
 line continuation character (i.e., "\").
 
 5. Some have suggested that JEdit may be a good editor 
 to have around for this and quick editing of Java files.
 It can save with Unix line endings.