Try this as a workaround...
Create the free product and place this in a hidden category. Insert the following code into one of the columns modules.
<ns:if condition="Cart.Total > 50">
DO STUFF HERE
...where 50 is the total of the cart and you can place a link or an image which links to the free product in the section that says do stuff here. This will allow that link to display whenever the customers cart total is greater than the value specified.
Some things to keep in mind if you did do this.
- You will want to make the maximum purchase for the free product 1 so they don't try and get more than one
- If anyone has access to the direct page they will be able to purchase the free product
I know this isn't the same way it worked with 4.x but it should work to do what you are wanting to.