Something doesn't work as expected. I added the line you suggested and restarted ispconfig server and apache server with no results.
To be true this is a symlink that starts from my directory:
lrwxrwxrwx 1 root root 25 2007-03-14 12:54 typo3_src -> /var/www/typo3_src-4.0.5/
this points to /var/www/typo3_src-4.0.5
I have another server with the previous version. There until added the following lines I can't use the /var/www/typo3_src-4.0.5/ contents (admin cpanel, ISP site->base):
php_admin_flag engine on
php_admin_flag safe mode off
php_admin_value open_basedir '/home/www/site.domain.it/web/:/tmp:/home/www/typo3_src'
In the new server this *not happens* and it is clear that /var/www is opened for all sites inside it...
Wainting for comments, thanx