Terms of Service on New Site Signup Page

I have been using a very old and outdated plugin that shows a terms of service the first time folks login: http://wordpress.org/extend/plugins/terms-of-use/

It is causing problems now, and I want to get on a regular updated plugin. I was looking at the terms of service plugin here. It seems like it would work, but our environment runs on shibboleth so there is no sign-up screen. They just log in.

I was thinking perhaps we could add it to the “New-Site” page and they would need to agree to the terms of service each time they created a site. Any ideas how I could add it to the /wp-signup.php page?

Thanks for any tips. I’d rather this were an option with the plugin so I could stay with y’all if you update rather than having to custom code it, but even pointing me in the right direction would be great.