JFBConnect doesn't have that built in, but there are a few ways to accomplish what you're looking for:
* JFBConnect has a mini-registration mode, where the user authenticates on a social network but then is brought to the profile page of your site to fill out any missing information. Here, you can add the checkbox or gather other details from the user. This makes registration a little longer and not 'one click', but would do what you're looking for. This mode works with Joomla's normal user registration page, Community Builder, JomSocial and EasySocial.
* When creating a Facebook application, you can provide your terms of service there. On the popup prompt to login to Facebook, it will provide a link to the terms and by authenticating, you're approving Facebook's terms and your sites.
I hope that helps explain, but if you get JFBConnect and need any further assistance, just let us know!