The files installed by the OSX installer .pkg should be group writable. 
This goes both for the files installed in /Library/Frameworks/
Python.framework and /Applications/MacPython-2.3

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This turns out to be non-trivial: the installed Python tree that is used to 
create the installer has group-write turned off, that's the way Python always 
installs the tree.

I could do a recursive chmod g+w before creating the installer, what do you 
think, would that be safe?

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Maybe my diagnosis is off. When I install (a non-framework) Python from the 
source, I don't use sudo, I just do "make install". In that case all files are 
owned by me. The installer however installs everything as root, and with the 
files being not group writable it means that I (even as an admin) can't move/
overwrite/delete the files without using sudo or changing the permissions.

I would expect to be able to have write permissions to the installed files if 
I'm an admin user. Don't know how to fix that easily, either.

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I think this is finally fixed. Could you do me a favor and test it? 
Just run Mac/OSX/Dist/build, remove your current /Library/
Frameworks/Python.framework and /Application/MacPython-2.3 
and try the installer built by "build".

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Some files are group writable, for group "admin", which is 
perfect. Some directories and Python.framework/Python are not.

However, I can throw away both the framework and the apps 
folder from the finder without problems, so it's not all bad...

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I give up. I now do a recursive chmod ug+w on the installed 
tree, and set umask to 2 before doing the compileall on the 
destination system. Please try again...