Ho provato a dare un occhio a quel link, al momento non ci capisco molto.
A mio avviso è un problema di apache, ho lo stesso problema anche con wordpress.
Provando nuovamente a installaere drupal ottengo questo messaggio:

Requirements problem
The following error must be resolved before you can continue the installation process:
The Drupal installer requires that you create a settings file as part of the installation process.

1. Copy the ./sites/default/default.settings.php file to ./sites/default/settings.php.
2. Change file permissions so that it is writable by the web server. If you are unsure how to grant file permissions, please consult the on-line handbook.

More details about installing Drupal are available in INSTALL.txt.
The following installation warning should be carefully reviewed:
Operations on Unicode strings are emulated on a best-effort basis. Install the PHP mbstring extension for improved Unicode support. (Currently using Unicode library Standard PHP)

Ma il file è già stato copiato e i permessi sono stati dati...