OLAT 6.3 introduced two ways to customize the disclaimer. You can add a second checkbox to the disclaimer and a link to a file download.
registration.disclaimerAdditionalCheckbox in olat.properties (olat.local.properties)
add the second checkbox. The label for this checkbox is in the i18n package org.olat.registration,
key disclaimer.additionalcheckbox.
registration.disclaimerAdditionaLinkText in olat.properties add
the link with the file download. The label is the i18n key disclaimer.filedownloadurl
in the package org.olat.registration. The path of the file relative to olatdata/customizing/disclaimer
is set with a i18n key disclaimer.filedownloadurl in the same package as the label.