I can reproduce this in the trunk, on OS X 10.5.1/Intel:  after a

./configure --enable-framework && make && sudo make altinstall

ctrl-clicking on a simple python file on the Desktop and selecting OpenWith -> PythonLauncher fails to run the 
script and gives essentially the same messages in the console:

1/30/08 7:59:31 PM Python Launcher[23508] doscript: Could not activate Terminal
1/30/08 7:59:31 PM Python Launcher[23508] doscript: AESend(activate): error -600
1/30/08 7:59:31 PM Python Launcher[23508] Exit status: -600

Assigning this to Ronald Oussoren since he was the last person to touch PythonLauncher, so probably has a much 
better idea than me of what's going on.

I'm a complete newbie when it comes to AppleEvents and the like, but I'm suspicious of the lines

#define ACTIVATE_CMD 'misc'
#define ACTIVATE_SUITE 'actv'

in Mac/PythonLauncher/doscript.m;  perhaps I'm looking in the wrong place, but I can't find documentation for 
'actv' anywhere.