PHP trouble after site transfer

I have a very limited knowledge of php so this is very challenging. This script was installed by a previous administrator and I’m trying to keep it working. It’s Phorm v3.0.4. Everything worked fine on the old server but not on dreamhost. I do have php enabled on the domain.
Here is a link to one of the forms. http://www.getaredbag.com/signup.htm
Hoping I’m missing something simple.
Thanks in advance

The extension on the script says “.php3”, which worries me. If it’s really written for PHP 3, the script you’re using is at least ten years out of date — PHP 4 was released in 2000, and it was itself replaced by PHP 5 in 2004.

Yea that was worrying me as well. The phorm search links on google are also dated[hr]
I’m just switching over the dreamweaver form