Araucaria works well on OS X. I think it was a setting in the
installation package that wasn't set correctly. Basically the
installation set the JVM version to 1.3 instead of 1.4 & OS X runs all
installed Java apps at v.1.3 unless otherwise specified. This should
only affect versions of OS X that have both versions 1.3.1 and later
installed. To remedy the situation: 

Ctrl-select( or right click) the Araucaria.app file and select "Show
Package Contents" from the menu. This will open a finder window.
Navigate into the contents folder and open the file "Info.plist" in a
text editor. Find the following entry: 

<key>Java</key>  
<dict>  
<key>MainClass</key>  
<string>YourApplication</string>  
<key>JVMVersion</key>  
<string>1.3*</string>  
<key>ClassPath</key>  
<string>$JAVAROOT/YourApplication.jar</string>  
</dict>  

and alter the JVMVersion's string value to 1.4*. Save and close the
file. Araucaria should now run when Application.app is clicked.