For JBT 3.2 development/nightly releases you can you can try to make it work using approach explained here http://www.eclipse.org/swt/faq.php#specifyxulrunner. Just get XULRunner 1.9.1.13 for macosx ppc from Geckpo Runtime Download site, unpack it somewhere in local file system and add system property
-Dorg.eclipse.swt.browser.XULRunnerPath=/path/to/xulrunner
to your eclipse.ini file as a new line somewhere after -vmargs.
Here is my eclipse.ini for test I did under linux x86 for JBT 3.2.0 nightly build.
-startup
plugins/org.eclipse.equinox.launcher_1.1.0.v20100507.jar
--launcher.library
plugins/org.eclipse.equinox.launcher.gtk.linux.x86_1.1.0.v20100503
-showsplash
org.eclipse.platform
--launcher.XXMaxPermSize
256m
--launcher.defaultAction
openFile
-vmargs
-Xms256m
-Xmx2048m
-Dorg.eclipse.swt.browser.XULRunnerPath=/home/eskimo/Java/xulrunner
Where /home/eskimo/Java/xulrunner is the path to the xulrunner runtime root folder which contains xulrunner shell script.