Cool!

I improved it a bit
In germany you have to accept both seperatly, the terms and the right of rescission (legal issue). So I made some checkboxes available in the admin panel, so that you can choose which of them should be displayed at checkout page.
I also made a textfield where you can enter the name of an PDF, that can be downloaded at the checkout page (thats also an obligation in germany).

@todo:
- make an upload field for the pdf instead of a text field
- check if the pdf-file exists
- play a little bit with jquery (see ryans comment)
- correct my english