Multiple installation of one ports

[FreeBSD]

Hi everyone,

I've been asked by a customer to install Drupal on one server to manage 
a new site. No problem yet. But, he also asked if it would be possible 
to install it for other sites.

I know that there is a warning if you want to install a port that is 
already installed, but is there a way to bypass this? I know I could 
install it from the tarball from the website, but I want to be able to 
use portupgrade and portaudit to deal with it.

Any suggestions?

Thank you for your time,

Martin