Message3337

I'm able to reproduce this.  sys.executable is not being set even though the 
launcher script sets the corresponding system property (-Dpython.executable=...)

Try changing the last line of the "jython" script to the following:

"/System/Library/Frameworks/JavaVM.framework/Versions/1.5.0/Home/bin/java" -
Dpython.home="/Users/xxx/Sites/jython2.5a1+" -classpath "$CP" 
org.python.util.jython -Dpython.executable="$0" "$@"

(replacing xxx with the directory where you have it installed).

-D arguments after the class specification are parsed by Jython rather than by the 
VM, and setting python.executable there works.

Another option (assuming you don't use it) is to move away or delete the "registry" 
file.

There are so many places to set Jython options (system properties, registry, 
Python-specific command line options, Jython-parsed -D options, and soon 
environment variables) it is really unclear how precedence should work; we should 
document this and make sure it's properly tested.