OsiAffiliate provides you complete custom solution to enable terms of services text for the signup page. There are following steps you can follow to Add Terms Text and then enable terms of services text for the sign up page.
First login to your admin control panel and click setup.
At setup page click settings and then Click the link says "Manage terms and Services Text"
At this Page you can type your Agreement terms and Conditions and click update.
Then go back to settings, scroll down and click "view advanced settings" link and check the box where it says "Require Terms and Services Acceptance"