No. Shopify doesn't allow apps to add a popup or checkbox to the checkout page itself. Terms:Pro works on your store's pages before checkout: it checks acceptance when customers click the purchase buttons you've turned on, such as Add to cart, Checkout on the cart page, Buy it now and express payment buttons.
To make sure no customer reaches checkout without accepting, keep all the buttons your theme shows turned on in the term's Options For Dynamic Checkout tab.
