I visited the official website of the developers and this is an answers to their FAQ questions:
Please go to the Product Selection page and select the product you are interested in. Please provide your contact details so that we can provide an installation password and provide technical support for your evaluation.
As you can see, you have to contact them in order to obtain an installation password to use with the current software. The problem is that no information could be found about FaultTree+ which means that it's either discontinued or its functionality is already embedded into their new products.