ITIL is not free, it is not a Public Domain framework.
Public Domain infers that the ITIL framework can be used freely in any manner, by anyone. However, this is not the case
The framework is copyright protected by the Office of Government Commerce (OGC) in the United Kingdom. The OGC has far reaching agreements in place with Governments around the world to help protect against unlawful use or reproduction.
The ITIL framework includes words and diagrams all are subject to copyright protection and only those organizations that have an official accreditation are permitted to use them in, for example, training materials