Simple clicking installatino works fine, there are just 2 scenarios for this error:

Scenario1:
Open shell and use
<path-to-1.6>/bin/java -jar jbdevstudio-product-eap-macosx-cocoa-x86_64-4.0.0.v201102161941R-H180-GA.ja
Try to install

Scenario2:
Open shell and use default (1.5) java and in installer change specific java to 1.6

You should see (and last-1 page in installer is empty):
main:
[echo] Run p2 metadata generator
[echo] jpeterka
[p2] Generating metadata for /home/brq/jpeterka/ide/jbds-4.0.0.ga-h180/studio.
[p2] Generation completed with success [0 seconds].
[delete] Deleting: /var/folders/zz/zzzivhrRnAmviuee++sVE+C6I/Tmp/artifacts.jar
[delete] Deleting: /var/folders/zz/zzzivhrRnAmviuee++sVE+C6I/Tmp/content.jar
java.lang.NullPointerException
at java.io.FileInputStream.<init>(FileInputStream.java:103)
at com.jboss.jbds.installer.CreateLinkPanel.addJREPath(CreateLinkPanel.java:176)
at com.jboss.jbds.installer.CreateLinkPanel.panelActivate(CreateLinkPanel.java:62)
at com.izforge.izpack.installer.InstallerFrame.switchPanel(Unknown Source)
at com.izforge.izpack.installer.InstallerFrame.navigateNext(Unknown Source)
at com.izforge.izpack.installer.InstallerFrame.navigateNext(Unknown Source)
at com.izforge.izpack.installer.InstallerFrame$NavigationHandler.actionPerformed(Unknown Source)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2028)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2351)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
at java.awt.Component.processMouseEvent(Component.java:6348)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
at java.awt.Component.processEvent(Component.java:6113)
at java.awt.Container.processEvent(Container.java:2085)
at java.awt.Component.dispatchEventImpl(Component.java:4714)
at java.awt.Container.dispatchEventImpl(Container.java:2143)
at java.awt.Component.dispatchEvent(Component.java:4544)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4618)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4282)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4212)
at java.awt.Container.dispatchEventImpl(Container.java:2129)
at java.awt.Window.dispatchEventImpl(Window.java:2475)
at java.awt.Component.dispatchEvent(Component.java:4544)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:635)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

calltarget: