Hi Leonardo,
I believe the plan is to eventually migrate all wikipedias over to the
PHP script. So your perspective and help from your side is very much
welcome.
You can read about the features of the new script at
http://wikipedia.com/wiki/wikipedia:PHP_script
and you can browse the current code at
http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/wikipedia/phpwiki/fpw/
To download the code, it's best to use anonymous CVS, explained on the
PHP_script page mentioned above.
Have fun,
Axel