I don't think you need a license for the Masher. Hot Potatoes (including the Masher) has been free to use since September 2009.
If you have already set up a chain of Hot Potatoes files - and maybe some other html files - in your Masher, you may want to try the QuizPort module for Moodle. It is the successor to the HotPot module. It is not part of the standard Moodle 1.9 download, but you can download it from the following location and install it on your Moodle site.
You can download the QuizPort module from here:
Introduction and manual (including installation instructions) are here: