We presume you want to capture at least a correct name and email for everyone obtaining your free product. The email especially is important to get complete and accurate, as that's where the thank-you email with any codes or download links would be sent, and where you would contact them as a prospective lead.
Thus, when someone is providing their info in our free checkout screen, if they hit Enter after filling a field instead of Tabbing or clicking into the next field, this would prevent completion of checkout when some information was incomplete.
Even when they complete all required fields, we still want to encourage them to at least glance back over it to make sure they entered everything correctly. We just had a chat about this here, and we decided to update the wording of that dialog to make the purpose of this clearer:
"If the info you provided looks correct, proceed with free checkout?"
BTW, this wording accounts for the fact that some browsers apparently offer OK/Cancel while others offer Yes/No, so either OK or Yes would confirm proceeding. :^)