My Mac has both the Apple Java 6 and Oracle Java 7 installed.
If I take the defaults from the JBDS Installer, allowing it to pick a Java 6 JRE, but then manually adding a server with Java 7 - the IDE fails to see that the server started.

Installation1.png - a screenshot of the defaults selected by the installer.
This places the following in my jbdevstudio.ini
-vm
/Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home/bin/java

and in About - Installation Details - Configuration:
-vm
/System/Library/Frameworks/JavaVM.framework

Adding a New Server (EAP 6 or 6.1) - but selecting Java 7 for the Runtime - is where the IDE fails to see that the server has started (runtime_JDK_7_selection.png)

The result is a failed start (failed_start.png)