Error message is "You must agree with the to get an account"

I discovered that this is because the error messaging relies upon the "Label for the fieldset" field on admin/settings/terms_of_use for it's variable. Given that this is a optional field and this is not really an optional message, this should be updated to:

1. Be a required field and explain it's various uses in the help text below the field.

- or -

2. Create a new field to be used as the identifier in the error message.